Trying to build the cross-compiler doesn't evaluate either:

$ nix-build -A pkgsCross.x86_64-unknown-redox.gcc13
...
       … from call site

         at /home/zmitchell/nixpkgs/pkgs/top-level/all-packages.nix:14930:16:

        14929|   gcc6Stdenv = overrideCC gccStdenv buildPackages.gcc6;
        14930|   gcc7Stdenv = overrideCC gccStdenv buildPackages.gcc7;
             |                ^
        14931|   gcc8Stdenv = overrideCC gccStdenv buildPackages.gcc8;

       … while calling 'overrideCC'

         at /home/zmitchell/nixpkgs/pkgs/stdenv/adapters.nix:35:24:

           34|   # Override the compiler in stdenv for specific packages.
           35|   overrideCC = stdenv: cc: stdenv.override {
             |                        ^
           36|     allowedRequisites = null;

       error: infinite recursion encountered

       at «none»:0: (source not available)