gcc: place cross-compiled target libraries in lib output

[lopsided98]

Motivation for this change

This is my take on an alternative, subjectively cleaner implementation of #58606 and #81781. The only functional difference is that the libraries are placed in $lib/$targetConfig/lib (which is the directory convention using by the GCC build scripts) rather than $lib/lib. This requires a minor change to cc-wrapper. Subjectively, I believe it is cleaner because it unifies the handling of the cross and non-cross cases and is therefore easier to reason about.

I have tested this change by building pkgsCross.armv7l-hf-multiplatform.hello and pkgsCross.aarch64-multiplatform.hello.

While searching for potential ramifications of this change, I found a patchelf invocation that is no longer needed. I have verified that the lib output of the native x86_64 builds of all supported GCC versions still contain no references to their corresponding out output after this change.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

cc @illegalprime @Floki @matthewbauer @eamsden

[lopsided98]

I removed the sotruss commit because I didn't see any references to build time bash. If someone thinks it is still needed, it can be included in a different PR.

[matthewbauer]

Yeah, this is definitely an improvement over the multi part if statements. If @illegalprime and @eamsden are okay with it, I'll merge this one and close out the other two.

[Ericson2314]

I hope someday the location of thtings can be the same for native and cross, but if it solves a real problem it is fine for now. The GCC build system is too much of a mess to fight slowly, it has to be an all or nothing attack.

[lopsided98]

@Ericson2314 Isn't your eventual goal to always cross-compile and use prefixed compilers (#44583 #21471), in which case this would be the correct solution and $targetConfig would be set even for native builds.

[Ericson2314]

@lopsided98 Yes, but my goal is also to build (or at least have build outputs as if we built) standard libraries like regular libraries, which means everything goes in $lib/lib. Given using GCC's monolithic build system, that would mean putting target vs host libs in separate outputs so they would both be in $output/lib.

[misuzu]

This probably broke i686 builds: https://hydra.nixos.org/build/114095842

[lopsided98]

#82510 should fix that.