zig: fix build

[wjlroe]

Motivation for this change

It looks like #88248 broke the
build for zig.

The error you get when building zig on the current master branch is:

Scanning dependencies of target zig_build_libstage2
: CommandLine Error: Option 'polly' registered more than once!
LLVM ERROR: inconsistency in registered CommandLine options
make[2]: *** [CMakeFiles/zig_build_libstage2.dir/build.make:77: CMakeFiles/zig_build_libstage2] Error 1
make[1]: *** [CMakeFiles/Makefile2:252: CMakeFiles/zig_build_libstage2.dir/all] Error 2
make: *** [Makefile:150: all] Error 2

The patch that added polly into some build args was likely necessary
only for LLVM 10.0.0 and when that was updated to 10.0.1 it stopped
working or became unnecessary. With this patch removed, zig builds fine
and passes the tests.

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.

[KAction]

I guess patch itself should be dropped too.

[sikmir]

Failed on darwin:

  [ 96%] Building CXX object CMakeFiles/zigcompiler.dir/src/os.cpp.o
  /private/var/folders/wf/qxrs82v946n91pb5s71n3dy80000gp/T/nix-build-zig-0.6.0.drv-0/source/src/os.cpp:1105:9: error: use of undeclared identifier 'futimens'
      if (futimens(file, times) == -1) {
          ^
  1 error generated.
  make[2]: *** [CMakeFiles/zigcompiler.dir/build.make:304: CMakeFiles/zigcompiler.dir/src/os.cpp.o] Error 1
  make[1]: *** [CMakeFiles/Makefile2:225: CMakeFiles/zigcompiler.dir/all] Error 2
  make: *** [Makefile:150: all] Error 2
cannot build derivation '/nix/store/7yngkkv0hszyjkqg4c7ahzbqga6wl9m7-env.drv': 1 dependencies couldn't be built

[wjlroe]

Failed on darwin:

  [ 96%] Building CXX object CMakeFiles/zigcompiler.dir/src/os.cpp.o
  /private/var/folders/wf/qxrs82v946n91pb5s71n3dy80000gp/T/nix-build-zig-0.6.0.drv-0/source/src/os.cpp:1105:9: error: use of undeclared identifier 'futimens'
      if (futimens(file, times) == -1) {
          ^
  1 error generated.
  make[2]: *** [CMakeFiles/zigcompiler.dir/build.make:304: CMakeFiles/zigcompiler.dir/src/os.cpp.o] Error 1
  make[1]: *** [CMakeFiles/Makefile2:225: CMakeFiles/zigcompiler.dir/all] Error 2
  make: *** [Makefile:150: all] Error 2
cannot build derivation '/nix/store/7yngkkv0hszyjkqg4c7ahzbqga6wl9m7-env.drv': 1 dependencies couldn't be built

Building zig on darwin looks like it'll remain broken until libSystem is updated and packages are built for a newer base system than macOS 10.12 (zig requires at least 10.13). So even on new macOSes, nixpkgs is building everything against an old libSystem I think. Details here: #86299

This PR won't affect darwin's build of Zig, it was broken before this and also broken before the update to LLVM 10.0.1

[wjlroe]

I guess patch itself should be dropped too.

Good point, I've deleted it, thanks