In preparation for the deprecation of `stdenv.isX`.
These shorthands are not conducive to cross-compilation because they
hide the platforms.
Darwin might get cross-compilation for which the continued usage of `stdenv.isDarwin` will get in the way
One example of why this is bad and especially affects compiler packages
https://www.github.com/NixOS/nixpkgs/pull/343059
There are too many files to go through manually but a treewide should
get users thinking when they see a `hostPlatform.isX` in a place where it
doesn't make sense.
```
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv.is" "stdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv'.is" "stdenv'.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "clangStdenv.is" "clangStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "gccStdenv.is" "gccStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenvNoCC.is" "stdenvNoCC.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "inherit (stdenv) is" "inherit (stdenv.hostPlatform) is"
fd --type f "\.nix" | xargs sd --fixed-strings "buildStdenv.is" "buildStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "effectiveStdenv.is" "effectiveStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "originalStdenv.is" "originalStdenv.hostPlatform.is"
```
When specifying the `builder` attribute in `stdenv.mkDerivation`, this
will be effectively transformed into
builtins.derivation {
builder = stdenv.shell;
args = [ "-e" builder ];
}
This also means that `default-builder.sh` is never sourced and as a
result it's not guaranteed that `$NIX_ATTRS_SH_FILE` is set to a correct
location[1].
Also, we need to source `.attrs.sh` to source `$stdenv`. So, the
following is done now:
* If `$NIX_ATTRS_SH_FILE` points to a correct location, then use it.
Directly using `.attrs.sh` is problematic for `nix-shell(1)` usage
(see previous commit for more context), so prefer the environment
variable if possible.
* Otherwise, if `.attrs.sh` exists, then use it. See [1] for when this
can happen.
* If neither applies, it can be assumed that `__structuredAttrs` is
turned off and thus nothing needs to be done.
[1] It's possible that it doesn't exist at all - in case of Nix 2.3 or
it can point to a wrong location on older Nix versions with a bug in
`__structuredAttrs`.
with structuredAttrs lists will be bash arrays which cannot be exported
which will be a issue with some patches and some wrappers like cc-wrapper
this makes it clearer that NIX_CFLAGS_COMPILE must be a string as lists
in env cause a eval failure
The configure script has changed and no longer seems to provide a way
to specify the location of the x11 libraries or headers. Therefore
these configure options have been dropped.
