darwin: introduce darwinArch, apply in {cc,bintools}-wrappers

[thefloweringash]

Motivation for this change

Extracted out of #105026. This, as well as #111988, try to make the darwin {cc,bintools}-wrappers use the correct flags for the target platform. A version of these flags previously existed only in the xcode wrapper.

Tested only as part of #105026. It changes the compiler and linker flags for all darwin packages, so there's a potential for a lot of breakage.

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.

[veprbl]

LGTM

[Ericson2314]

Great!

[bobrik]

Looks like it broke stdenv on x86_64-darwin:

clang-7: error: cannot use 'cpp-output' output with multiple -arch options
mig: fatal: "<no name yet>", line -1: no SubSystem declaration
make[2]: *** [Makefile:754: kcmrpc.h] Error 1
make[2]: Leaving directory '/private/tmp/nix-build-libkrb5-1.18.drv-0/krb5-1.18/src/lib/krb5/ccache'
make[1]: *** [Makefile:1154: all-recurse] Error 1
make[1]: Leaving directory '/private/tmp/nix-build-libkrb5-1.18.drv-0/krb5-1.18/src/lib/krb5'
make: *** [Makefile:1004: all-recurse] Error 1
builder for '/nix/store/hawwz9cvywyqsn3180cl3afnpf7k47y0-libkrb5-1.18.drv' failed with exit code 2
building '/nix/store/y269ail4wsxszqgszhx00nsph44gsyhw-binutils-2.35.1.drv'...
cannot build derivation '/nix/store/fgxnwij7bnq1iw4c581ndaiyxd3d5a38-bootstrap-stage2-stdenv-darwin.drv': 1 dependencies couldn't be built

[thefloweringash]

Looks like it broke stdenv on x86_64-darwin:

I was so sure it had been tested as part of the apple-silicon branch. I'm building staging now to debug. I'm hoping it'll be fixed by the commit titled darwin.bootstrap_cmds: use correct arch in "mig".

[bobrik]

@thefloweringash looks like thefloweringash@178ad9a indeed fixes the issue.

[thefloweringash]

@thefloweringash looks like thefloweringash@178ad9a indeed fixes the issue.

Excellent! Thank you for testing.

I've opened this as #114944.

[thefloweringash]

This broke llvmPackages_11.compiler-rt and the problem seems to come from the intermediate .a archives having multiple architectures. More broadly, I think this PR will interfere with universal binaries and compiler-rt just happens to be the one I noticed. I infer that -arch flags combine, which means this should be providing a default value, not always passing a value.