cc-wrapper: remove quoting of response file

[thefloweringash]

Fixes build failures with clang:

clang-7: error: unknown argument: '-fPIC                -target'
clang-7: error: no such file or directory: '@<(printf %qn        -O2'
clang-7: error: no such file or directory: 'x86_64-apple-darwin'

Introduced by 60c5cf9 in #112449

Motivation for this change

Fix darwin stdenv on staging-next.

The problem is present on both staging and staging-next, and I don't know which branch to send this to so I picked one.

cc @angerman @matthewbauer

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.

[Mic92]

We merge staginx-next into staging automatically every six hours.