To work around intermitent build failures with clang 16, the stdenv
attempted to pass arguments on the command-line on newer versions of
macOS. Unfortunately, the larger `ARG_MAX` is still not large enough to
build qtwebengine. This commit reverts the `NIX_CC_NO_RESPONSE_FILE`
logic in the stdenv. The changes to cc-wrapper in #245282 are needed for
clang 16 to prevent the above-mentioned build failures.
This fixes pyicu (and any other package that uses `icu-config` instead
of the CMake or some other module to get the build flags).
What happened here is the bootstrap disables `patchShebangs` to avoid
propagating the bootstrap tools to the final stdenv (due to `sh` and
`bash` being on the `PATH` from the bootstrap tools). Because of that,
the `#!/bin/sh` line in `icu-config` was not updated, causing it to
invoke the system bash on Darwin. While that is undesirable in its own
right, when the system bash is invoked as `sh`, `echo -n` will print
`-n`, resulting in the breakage see in https://github.com/NixOS/nixpkgs/pull/241951#issuecomment-1627604354.
The fix is to build bash earlier in the bootstrap while making sure it
is picked up over the one in the bootstrap tools. That allows
`patchShebangs` to be enabled during the bootstrap. Any package with
scripts that is included in the final stdenv should now have its
scripts’ shebang lines properly patched.
When sandboxing is enabled, the hook tries to run `install_name_tool`
and fails because the system one is inaccessible. Having it use
`targetPrefix` allows it to find and use the cross-install_name_tool.
swift-corelibs uses libcurl to implement `NSURLSession` in Foundation
via the symbols exported by CF. Foundation is not build on Darwin, and
these symbols are not exported by the system CoreFoundation.
By not linking against libcurl, this breaks a cycle between CF and
libcurl. That should allow libcurl to drop the patch disabling
linking against the SystemConfiguration and restore NAT64 support.
Unfortunately, the Darwin stdenv bootstrap still needs to build
dependencies that use `fetchFromGitHub`. While it can drop curl from the
final stdenv, it still needs to use it during the stdenv bootstrap.
In preparation for bumping the LLVM used by Darwin, this change
refactors and reworks the stdenv build process. When it made sense,
existing behaviors were kept to avoid causing any unwanted breakage.
However, there are some differences. The reasoning and differences are
discussed below.
- Improved cycle times - Working on the Darwin stdenv was a tedious
process because `allowedRequisites` determined what was allowed
between stages. If you made a mistake, you might have to wait a
considerable amount of time for the build to fail. Using assertions
makes many errors fail at evaluation time and makes moving things
around safer and easier to do.
- Decoupling from bootstrap tools - The stdenv build process builds as
much as it can in the early stages to remove the requirement that the
bootstrap tools need bumped in order to bump the stdenv itself. This
should lower the barrier to updates and make it easier to bump in the
future. It also allows changes to be made without requiring additional
tools be added to the bootstrap tools.
- Patterned after the Linux stdenv - I tried to follow the patterns
established in the Linux stdenv with adaptations made to Darwin’s
needs. My hope is this makes the Darwin stdenv more approable for
non-Darwin developers who made need to interact with it. It also
allowed some of the hacks to be removed.
- Documentation - Comments were added explaining what was happening and
why things were being done. This is particular important for some
stages that might not be obvious (such as the sysctl stage).
- Cleanup - Converting the intermediate `allowedRequisites` to
assertions revealed that many packages were being referenced that no
longer exist or have been renamed. Removing them reduces clutter and
should help make the stdenv bootstrap process be more understandable.
cctools-llvm is a replacement for cctools that replaces as much of cctools with equivalents from LLVM that it can reasonably do. This was motivated by wanting to reduce dependencies on cctools, which are updated infrequently by upstream.
To provide a motivating example, the version of `strip` included in cctools cannot properly strip the archives in compiler-rt in LLVM 15. Paths are left to bootstrap tools, resulting in failed requisites checks in the final stdenv build. Since `strip` needs replaced, the opportunity was taken to replace other provided they are functional replacements.
Note: This has to be done in cctools (or some equivalent) because some derivations (noteably LLVM) use the bintools of the stdenv directly instead of going through the wrapper.
The following tools from LLVM are not used in this derivation:
* LLD - not fully compatible with ld64 yet and potentially too big of a change;
* libtool - not a drop-in replacement yet because it does not support linker passthrough, which is needed by xcbuild;
* lipo - crashes when running the LLVM test suite;
* install_name_tool - fails when trying to build swift-corefoundation; and.
* randlib - not completely a drop-in replacement, so leaving it out for now.
If other incompatabilities are found, the tools can be reverted or made conditional. For example, cctools `strip` is preferred on older versions of LLVM (which lack the compiler-rt issue) or when cctools itself is a new enough version because `llvm-strip` on LLVM 11 produces files that older verions of `codesign_allocate` cannot process correctly.
One final caveat/note: Some tools are not duplicated or linked from cctools-port. The names of the tools and which ones were linked was determined based on what is provided upstream in Xcode and is installed on macOS system.
The stdenv wouldn't build with it, as
compiler-rt-libc-11.1.0/lib/darwin/libclang_rt.*_osx.a
retained reference to SDKs (which we forbid for final stdenv).
Assigned authorship to Trofi; I just bisected and added condition.
https://github.com/NixOS/nixpkgs/pull/224669#issuecomment-1518225496
A few potentially disruptive changes:
- binutils does not embed ${binutils-unwrapped}/lib as a default library
search path anymore. This will cause link failures for -lbfd -lopcodes
users that did not declare their dependency on those libraries. They
will need to add `libbfd` and `libopcodes` attributes to build inputs.
- `libbfd` and `libopcodes` attributes now just reference
`binutils-unwrapped.{dev,lib}` pair of attributes without patching
`binutils` build system.
We don't patch build system anymore and use multiple outputs out of
existing `binutils` build. That makes the result more maintainable: no
need to handle ever growing list of dependencied of `libbfd`. This time
new addition was `libsframe`.
To accomodate `out` / `lib` output split I had to remove `lib` -> `bin`
backreference by removing legacy lookup path for plugins.
I also did not enable `zstd` just yet as `nixpkgs` version of `zstd`
package pulls in `cmake` into bootstrap sequence.
Changes: https://lists.gnu.org/archive/html/info-gnu/2023-01/msg00003.html
FreeBSD doesn't use LLVM's cxxabi implementation, for backwards
compatibility reasons. Software expects the libcxxrt API when
building on FreeBSD. This fixes the build of
pkgsCross.x86_64-freebsd.boost.
Stdenv on aarch64-darwin pulls in (bootstrap-stage4) objc4, unlike
x86_64. However derivations that otherwise depend on objc4 would use a
a different objc4 derivation on top of the final stdenv.
Because this library defines an LLVM module, having multiple instances
of it in the import path will interfere with builds.
It's expected that attributes in the top-level package set will all use
that package set, but this wasn't the case for the bootstrap tools.
This led some very confusing behaviour:
- pkgsMusl.stdenvBootstrapTools would build glibc bootstrap tools
- stdenvBootstrapTools was _always_ cross compiled, even if
Nixpkgs wasn't, because it always set crossSystem. This also didn't
match the behaviour of using make-bootstrap-tools.nix as an
entrypoint, where crossSystem would default to null.
For the Linux stdenv, I've made the ideal fix, which is to make pkgs an
argument rather than taking the arguments for pkgs, and then
re-importing it. This means it'll always use exactly the same package
set that's calling it, and should also mean faster eval due to not
importing Nixpkgs twice.
The Darwin stdenv is more complicated, and I'm not able to easily test
it, so I wasn't confident in making the same fix there. Instead, I've
just made sure crossSystem and localSystem are set to the correct values
so they're not always cross compiled and match the parent package set's.
It would still be preferable if somebody could make Darwin's
make-bootstrap-tools.nix take pkgs as an argument, rather than all the
arguments for pkgs.
libtool's libtool.m4 script assumes that `file` is available, and can
be found at `/usr/bin/file` (this path is hardwired). Furthermore,
the script with this assumption is vendored into the ./configure
scripts of an enormous number of packages. Without this commit, you
will frequently see errors like this during the configurePhase with
the sandbox enabled:
./configure: line 9595: /usr/bin/file: command not found
Due mostly to luck, this error does not affect native compiles on
nixpkgs' two most popular platforms, x86_64-linux and aarch64-linux.
However it will cause incorrect linker flag detection and a failure to
generate shared libraries for sandboxed cross-builds to a x86_64-linux
host as well as any sandboxed build (cross or native) for the following
hosts: x86_64-freebsd, *-hpux, *-irix, mips64*-linux, powerpc*-linux,
s390x-linux, s390x-tpf, sparc-linux, and *-solaris.
This commit fixes the problem by adding an extra line to fixLibtool()
in pkgs/stdenv/generic/setup.sh. This extra line will scan the
unpacked source code for executable files named "configure" which
contain the following text:
'GNU Libtool is free software; you can redistribute it and/or modify'
This text is taken to be an indicator of a vendored libtool.m4. When
it is found, the configure script containing it is subjected to `sed
-i s_/usr/bin/file_file_` which replaces all occurrences of
`/usr/bin/file` with `file`.
Additionally, the `file` package is now considered to be part of
`stdenv`. It has been added to `common-path.nix` so that the `file`
binary will be found in the `$PATH` of every build, except for the
bootstrap-tools and the first few stages of stdenv boostrapping.
Verified no regressions under:
nix-build --arg pkgs 'import ./. {}' ./lib/tests/release.nix
This commit allows the following commands to complete, which should
enable Hydra to produce bootstrap-files for mips64el:
nix-build \
--option sandbox true \
--option sandbox-fallback false \
pkgs/top-level/release-cross.nix \
-A bootstrapTools.mips64el-linux-gnuabi64.build
nix-build \
--option sandbox true \
--option sandbox-fallback false \
. \
-A pkgsCross.mips64el-linux-gnuabi64.nix_2_4
At some point, I'd like to make another attempt at
71f1f4884b ("openssl: stop static binaries referencing libs"), which
was reverted in 195c7da07d. One problem with my previous attempt is
that I moved OpenSSL's libraries to a lib output, but many dependent
packages were hardcoding the out output as the location of the
libraries. This patch fixes every such case I could find in the tree.
It won't have any effect immediately, but will mean these packages
will automatically use an OpenSSL lib output if it is reintroduced in
future.
This patch should cause very few rebuilds, because it shouldn't make
any change at all to most packages I'm touching. The few rebuilds
that are introduced come from when I've changed a package builder not
to use variable names like openssl.out in scripts / substitution
patterns, which would be confusing since they don't hardcode the
output any more.
I started by making the following global replacements:
${pkgs.openssl.out}/lib -> ${lib.getLib pkgs.openssl}/lib
${openssl.out}/lib -> ${lib.getLib openssl}/lib
Then I removed the ".out" suffix when part of the argument to
lib.makeLibraryPath, since that function uses lib.getLib internally.
Then I fixed up cases where openssl was part of the -L flag to the
compiler/linker, since that unambigously is referring to libraries.
Then I manually investigated and fixed the following packages:
- pycurl
- citrix-workspace
- ppp
- wraith
- unbound
- gambit
- acl2
I'm reasonably confindent in my fixes for all of them.
For acl2, since the openssl library paths are manually provided above
anyway, I don't think openssl is required separately as a build input
at all. Removing it doesn't make a difference to the output size, the
file list, or the closure.
I've tested evaluation with the OfBorg meta checks, to protect against
introducing evaluation failures.
The `curlMinimal` is to be used throughout the early bootstrap
stages. The final stage will allow the new references of the `curl`.
Fixes: 29526bc2 ('curl: IDN support requires libidn2 package')
`TargetConditionals.h` was missing several definitions, like
`TARGET_OS_TV` that are part of SDK 10.12 at least. And one that doesn't
seem to occur in any SDK afaict, `TARGET_OS_EMBEDDED_OTHER`.
I added the definitions from SDK 10.12 verbatim and defined
`TARGET_OS_EMBEDDED_OTHER` to be equal to `0`.
I think none of this works if `darwin.Libsystem` is used to build for
linux or iOS though so maybe this needs a more thorough fix?
This reverts 336d82617f because it's no
longer necessary.
This enables the bootstrap stdenv test to specify the actual llvm
of the newly generated build instread of assuming it's the same version
as the current stdenv.
Changes to llvmPackages have caused the `libclang-cpp*.dylib` files to
be included in the `clang-unwrapped.lib` output. So we no longer need to
copy them from libclang.
`TargetConditionals.h` was missing several definitions, like
`TARGET_OS_TV` that are part of SDK 10.12 at least. And one that doesn't
seem to occur in any SDK afaict, `TARGET_OS_EMBEDDED_OTHER`.
I added the definitions from SDK 10.12 verbatim and defined
`TARGET_OS_EMBEDDED_OTHER` to be equal to `0`.
This is a modified version of a patch to avoid a stdenv rebuild.
I was having a hard time testing new bootstrapFiles because
`make-bootstrap-tools.nix` imports `pkgspath` but does not pass anything
but the current system.
This is merely for convenience and I'm not entirely certain it's a
sensible thing to do, maybe generating new bootstrapFiles while
overriding the current bootstrapFiles isn't something you're supposed to
do?
The rpath structure for the bootstrap tools was reworked to minimize
the amount of rewriting required on unpack, but the test was not
updated to match the different structure.
Additionally [1] builds that use the bootstrap version of libc++
cannot find libc++abi if the reference includes the "lib"
component (ie, libc++ refers to libc++abi with
@rpath/lib/libc++abi.dylib).
[1] https://logs.nix.samueldr.com/nix-darwin/2021-05-18#4993282
Test failure observed on Hydra: https://hydra.nixos.org/build/143130126
If things build fine with `stdenvNoCC`, let them use that. If tools
might be prefixed, prepare for that, either by directly splicing or just
using the env vars provided by the wrapper setup-hooks.
Co-authored-by: Dmitry Kalinkin <dmitry.kalinkin@gmail.com>
I am taking the non-invasive parts of #110914 to hopefully help out with #111988.
In particular:
- Use `lib.makeScopeWithSplicing` to make the `darwin` package set have
a proper `callPackage`.
- Adjust Darwin `stdenv`'s overlays keeping things from the previous
stage to not stick around too much.
- Expose `binutilsNoLibc` / `darwin.binutilsNoLibc` to hopefully get us
closer to a unified LLVM and GCC bootstrap.
Also begin to start work on cross compilation, though that will have to
be finished later.
The patches are based on the first version of
https://reviews.llvm.org/D99484. It's very annoying to do the
back-porting but the review has uncovered nothing super major so I'm
fine sticking with what I've got.
Beyond making the outputs work, I also strove to re-sync the packages,
as they have been drifting pointlessly apart for some time.
----
Other misc notes, highly incomplete
- lvm-config-native and llvm-config are put in `dev` because they are
tools just for build time.
- Clang no longer has an lld dep. That was introduced in
db29857eb3, but if clang needs help
finding lld when it is used we should just pass it flags / put in the
resource dir. Providing it at build time increases critical path
length for no good reason.
----
A note on `nativeCC`:
`stdenv` takes tools from the previous stage, so:
1. `pkgsBuildBuild`: `(?1, x, x)`
2. `pkgsBuildBuild.stdenv.cc`: `(?0, ?1, x)`
while:
1. `pkgsBuildBuild`: `(?1, x, x)`
2. `pkgsBuildBuild.targetPackages`: `(x, x, ?2)`
3. `pkgsBuildBuild.targetPackages.stdenv.cc`: `(?1, x, x)`
Patch every `derivation` call in the bootsrap process to add it a
conditional `__contentAddressed` parameter.
That way, passing `contentAddressedByDefault` means that the entire
build closure of a system can be content addressed
Build the llvm support libraries (libcxx, libcxxabi) from scratch
without using the existing llvm libraries. This is the same spirit and
similar implementation as the "useLLVM" bootstrap in llvm package
sets. Critically it avoids having libcxxabi provided by the cc-wrapper
when building libcxx, which otherwise results in two libcxxabi
instances.
$ otool -L /nix/store/vd4vvgs9xngqbjzpg3qc41wl6jh42s9i-libc++-7.1.0/lib/libc++.dylib
/nix/store/vd4vvgs9xngqbjzpg3qc41wl6jh42s9i-libc++-7.1.0/lib/libc++.dylib:
/nix/store/vd4vvgs9xngqbjzpg3qc41wl6jh42s9i-libc++-7.1.0/lib/libc++.1.0.dylib (compatibility version 1.0.0, current version 1.0.0)
/nix/store/gmpwk5fyp3iasppqrrdpswxvid6kcp8r-libc++abi-7.1.0/lib/libc++abi.dylib (compatibility version 1.0.0, current version 1.0.0)
/nix/store/3hn7azynqgp2pm5gpdg45gpq0ia72skg-libc++abi-7.1.0/lib/libc++abi.dylib (compatibility version 1.0.0, current version 1.0.0)
/nix/store/1nq94scbxs6bk7pimqhvz76q6cfmbv97-Libsystem-osx-10.12.6/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1226.10.1)
Additionally move some utilities (clang, binutils, coreutils, gnugrep)
to the stage layers so they can be replaced before the final
stdenv. This should cause most of stage4 to be built from the
toolchain assembled as of stage3 instead of the bootstrap toolchain.
This new version has tapi support, which is needed to build the new
stubs based libSystem, etc. and Big Sur support.
You can verify the provenance of these yourself by checking Hydra here:
https://hydra.nixos.org/build/128192471
This reverts commit c778945806.
I believe this is exactly what brings the staging branch into
the right shape after the last merge from master (through staging-next);
otherwise part of staging changes would be lost
(due to being already reachable from master but reverted).
The Rust `cc` crate started running `xcrun` when SDKROOT is defined:
a970b0ab0b
Consequently, building crates that use newer versions of the `cc`
crate fail, because xcrun is not available in pure build environments.
Fixes#21629
Passing these extra linker flags removes both the semi-random uuid
included in most binaries as well as making the sdk version consistent
instead of based on the current os version.
Load command 8
cmd LC_UUID
cmdsize 24
uuid 70FAF921-5DC8-371C-B814-4F121FADFDF4
Load command 9
cmd LC_VERSION_MIN_MACOSX
cmdsize 16
version 10.12
sdk 10.13
The -macosx_version_min flag isn't strictly necessary since that's
already handled by MACOSX_DEPLOYMENT_TARGET.
- Replaced python override from the final stdenv, instead we
propagate our bootstrap python to stage4 and override both
CF and xnu to use it.
- Removed CF argument from python interpreters, this is redundant
since it's not overidden anymore.
- Inherit CF from stage4, making it the same as the stdenv.
Adds the static overlay that can be used to build Nixpkgs statically.
Can be used like:
nix build pkgsStatic.hello
Not all packages build, as some rely on dynamic linking.
crossOverlays only apply to the packages being built, not the build
packages. It is useful when you don’t care what is used to build your
packages, just what is being built. The idea relies heavily on the
cross compiling infrastructure. Using this implies that we need to
create a cross stdenv.
02c09e0171 (NixOS/nixpkgs#44558) was reverted in
c981787db9 but, as it turns out, it fixed an issue
I didn't know about at the time: the values of `propagateDoc` options were
(and now again are) inconsistent with the underlying things those wrappers wrap
(see NixOS/nixpkgs#46119), which was (and now is) likely to produce more instances
of NixOS/nixpkgs#43547, if not now, then eventually as stdenv changes.
This patch (which is a simplified version of the original reverted patch) is the
simplest solution to this whole thing: it forces wrappers to directly inspect the
outputs of the things they are wrapping instead of making stdenv guess the correct
values.
This accidentally added some unwanted dependencies on the bootstrap
tools, and I don't have time to fix before I go on vacation, so I'm
backing it out until I have time to address it properly.
This reverts commit dc5c68a7bb.
LTO is disabled during bootstrap to keep the bootstrap tools small and
avoid unnecessary LLVM rebuilds, but is enabled in the final stdenv
stage and should be usable by normal packages.
This also updates the bootstrap tool builder to LLVM 5, but not the ones
we actually use for bootstrap. I'll make that change in a subsequent commit
so as to provide traceable provenance of the bootstrap tools.
On darwin llvmPackages is built using python-boot to avoid dependencies
in the stdenv, but we can't and shouldn't use that when building the
manpages since it depends on python packages.
* substitute(): --subst-var was silently coercing to "" if the variable does not exist.
* libffi: simplify using `checkInputs`
* pythonPackges.hypothesis, pythonPackages.pytest: simpify dependency cycle fix
* utillinux: 2.32 -> 2.32.1
https://lkml.org/lkml/2018/7/16/532
* busybox: 1.29.0 -> 1.29.1
* bind: 9.12.1-P2 -> 9.12.2
https://ftp.isc.org/isc/bind9/9.12.2/RELEASE-NOTES-bind-9.12.2.html
* curl: 7.60.0 -> 7.61.0
* gvfs: make tests run, but disable
* ilmbase: disable tests on i686. Spooky!
* mdds: fix tests
* git: disable checks as tests are run in installcheck
* ruby: disable tests
* libcommuni: disable checks as tests are run in installcheck
* librdf: make tests run, but disable
* neon, neon_0_29: make tests run, but disable
* pciutils: 3.6.0 -> 3.6.1
Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools. This update was made based on information from https://repology.org/metapackage/pciutils/versions.
* mesa: more include fixes
mostly from void-linux (thanks!)
* npth: 1.5 -> 1.6
minor bump
* boost167: Add lockfree next_prior patch
* stdenv: cleanup darwin bootstrapping
Also gets rid of the full python and some of it's dependencies in the
stdenv build closure.
* Revert "pciutils: use standardized equivalent for canonicalize_file_name"
This reverts commit f8db20fb3a.
Patching should no longer be needed with 3.6.1.
* binutils-wrapper: Try to avoid adding unnecessary -L flags
(cherry picked from commit f3758258b8895508475caf83e92bfb236a27ceb9)
Signed-off-by: Domen Kožar <domen@dev.si>
* libffi: don't check on darwin
libffi usages in stdenv broken darwin. We need to disable doCheck for that case.
* "rm $out/share/icons/hicolor/icon-theme.cache" -> hicolor-icon-theme setup-hook
* python.pkgs.pytest: setupHook to prevent creation of .pytest-cache folder, fixes#40273
When `py.test` was run with a folder as argument, it would not only
search for tests in that folder, but also create a .pytest-cache folder.
Not only is this state we don't want, but it was also causing
collisions.
* parity-ui: fix after merge
* python.pkgs.pytest-flake8: disable test, fix build
* Revert "meson: 0.46.1 -> 0.47.0"
With meson 0.47.0 (or 0.47.1, or git)
things are very wrong re:rpath handling
resulting in at best missing libs but
even corrupt binaries :(.
When we run patchelf it masks the problem
by removing obviously busted paths.
Which is probably why this wasn't noticed immediately.
Unfortunately the binary already
has a long series of paths scribbled
in a space intended for a much smaller string;
in my testing it was something like
lengths were 67 with 300+ written to it.
I think we've reported the relevant issues upstream,
but unfortunately it appears our patches
are what introduces the overwrite/corruption
(by no longer being correct in what they assume)
This doesn't look so bad to fix but it's
not something I can spend more time on
at the moment.
--
Interestingly the overwritten string data
(because it is scribbled past the bounds)
remains in the binary and is why we're suddenly
seeing unexpected references in various builds
-- notably this is is the reason we're
seeing the "extra-utils" breakage
that entirely crippled NixOS on master
(and probably on staging before?).
Fixes#43650.
This reverts commit 305ac4dade.
(cherry picked from commit 273d68eff8)
Signed-off-by: Domen Kožar <domen@dev.si>
We already did them on non-mass-rebuild llvm 6. Also, this allows
simplifying the stdenv booting.
We were missing the libcxxabi dep in compile-rt in llvm 6, so fixed that
too.
It may seem nice and abstract to just override the default version, but
that breaks the alias relationship where the original llvmPackages_* is
no longer in sync. Put another away, modifying the referee rather
instead of breaking the reference "copy-on-write" is impossible.
Since at least d7bddc27b2, we've had a
situation where one should depend on:
- `stdenv.cc.bintools`: for executables at build time
- `libbfd` or `libiberty`: for those libraries
- `targetPackages.cc.bintools`: for exectuables at *run* time
- `binutils`: only for specifically GNU Binutils's executables,
regardless of the host platform, at run time.
and that commit cleaned up this usage to reflect that. This PR flips the
switch so that:
- `binutils` is indeed unconditionally GNU Binutils
- `binutils-raw`, which previously served that role, is gone.
so that the correct usage will be enforced going forward and everything
is simple.
N.B. In a few cases `binutils-unwrapped` (which before and now was
unconditionally actual GNU binutils), rather than `binutils` was used to
replace old `binutils-raw` as it is friendly towards some cross
compilation usage by avoiding a reference to the next bootstrapping
change.
For the cc of the intermediate stages, to be precise. Doing the same for
bintools requires lots of refactoring.
This is mainly for the future extensibility as now you can change
documentation generation with impunity without rebuilding the
whole of stdenv.
