lld needs LLVM's libunwind for its headers. That libunwind is not part
of the tools scope in pkgs/development/compilers/llvm/12/default.nix,
which means that lld previously received libunwind from top-level pkgs
which of course doesn't have the required headers.
To resolve this pass libunwind from the libraries scope — platform
concerns don't really mattern as only libunwind.src is used.
libunwind was initially passed correctly, but that was removed in
e830db4320. This regression was likely
introduced accidentally.
The bintools argument received a wrapped version of tools.bintools which
is already wrapped. Wrapped bintools twice leads to users of lldClang
being unable to find the tools which are not wrapped like ar.
The main thing was using `llvm_meta` in all versions.
Secondarily:
- libunwindx7: Forgot to split outputs
- libcxx{,abi} 12: Forgot to apply output-splitting patches.
- simplify `useLLVM` stdenv-switching logic.
- openmp always gets its own directory
- Introduce `preLibcCrossHeaders` to bootstrap libgcc and compiler-rt
the same way.
- Organize LLVM bintools as `bintools{-unwrapped,,NoLibc}` for
consistency with GNU Binutils and Apple's cctools.
- Do Android changes for all `llvmPackages` for consistency.
- Improve the way the default GCC and LLVM versions are selected.
This PR adds a new aarch64 android toolchain, which leverages the
existing crossSystem infrastructure and LLVM builders to generate a
working toolchain with minimal prebuilt components.
The only thing that is prebuilt is the bionic libc. This is because it
is practically impossible to compile bionic outside of an AOSP tree. I
tried and failed, braver souls may prevail. For now I just grab the
relevant binaries from https://android.googlesource.com/.
I also grab the msm kernel sources from there to generate headers. I've
included a minor patch to the existing kernel-headers derivation in
order to expose an internal function.
Everything else, from binutils up, is using stock code. Many thanks to
@Ericson2314 for his help on this, and for building such a powerful
system in the first place!
One motivation for this is to be able to build a toolchain which will
work on an aarch64 linux machine. To my knowledge, there is no existing
toolchain for an aarch64-linux builder and an aarch64-android target.
In 7869d16545 I got rid of the symlinking
by forcing `COMPILER_RT_OS_DIR` to always be the empty string. I thought
this was good because it just make compiler-rt be installed in a normal
way.
However, various LLVM tools expect the `COMPILER_RT_OS_DIR` to be set
normally, and fail to find things when they aren't in the expected lib
subdir.
Maybe it would be best to patch that too in the long term, but for now
we just undo this change.
