tests.cc-wrapper.supported: make it actually build the tests

      name = "cc-wrapper-supported";

      builtGCC =

        let

          names = lib.pipe (attrNames gccTests) ([

            (filter (n: lib.meta.availableOn stdenv.hostPlatform pkgs.${n}.cc))

          inherit (lib) filterAttrs;

          sets = lib.pipe gccTests ([

            (filterAttrs (_: v: lib.meta.availableOn stdenv.hostPlatform v.stdenv.cc))

            # Broken

            (filter (n: n != "gcc49Stdenv"))

            (filter (n: n != "gccMultiStdenv"))

            (filterAttrs (n: _: n != "gcc49Stdenv"))

            (filterAttrs (n: _: n != "gccMultiStdenv"))

          ] ++ lib.optionals (stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isAarch64) [

            # fails with things like

            # ld: warning: ld: warning: object file (trunctfsf2_s.o) was built for newer macOS version (11.0) than being linked (10.5)

            # ld: warning: ld: warning: could not create compact unwind for ___fixunstfdi: register 20 saved somewhere other than in frame

            (filter (n: n != "gcc11Stdenv"))

            (filterAttrs (n: _: n != "gcc11Stdenv"))

          ]);

        in

        toJSON (lib.genAttrs names (name: { name = pkgs.${name};  }));

        toJSON sets;

      builtLLVM =

        let

          names = lib.pipe (attrNames llvmTests) ([

            (filter (n: lib.meta.availableOn stdenv.hostPlatform pkgs.${n}.stdenv.cc))

            (filter (n: lib.meta.availableOn stdenv.hostPlatform pkgs.${n}.libcxxStdenv.cc))

          inherit (lib) filterAttrs;

          sets = lib.pipe llvmTests ([

            (filterAttrs (_: v: lib.meta.availableOn stdenv.hostPlatform v.clang.stdenv.cc))

            (filterAttrs (_: v: lib.meta.availableOn stdenv.hostPlatform v.libcxx.stdenv.cc))

            # libcxxStdenv broken

            # fix in https://github.com/NixOS/nixpkgs/pull/216273

          ] ++ lib.optionals (stdenv.hostPlatform.isLinux && stdenv.hostPlatform.isAarch64) [

            # libcxx does not build for some reason on aarch64-linux

            (filter (n: n != "llvmPackages_7"))

            (filterAttrs (n: _: n != "llvmPackages_7"))

          ] ++ lib.optionals (stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isAarch64) [

            (filter (n: n != "llvmPackages_5"))

            (filter (n: n != "llvmPackages_6"))

            (filter (n: n != "llvmPackages_7"))

            (filter (n: n != "llvmPackages_8"))

            (filter (n: n != "llvmPackages_9"))

            (filter (n: n != "llvmPackages_10"))

            (filterAttrs (n: _: n != "llvmPackages_5"))

            (filterAttrs (n: _: n != "llvmPackages_6"))

            (filterAttrs (n: _: n != "llvmPackages_7"))

            (filterAttrs (n: _: n != "llvmPackages_8"))

            (filterAttrs (n: _: n != "llvmPackages_9"))

            (filterAttrs (n: _: n != "llvmPackages_10"))

          ]);

        in

        toJSON (lib.genAttrs names (name: { stdenv = pkgs.${name}.stdenv; libcxx = pkgs.${name}.libcxxStdenv;  }));

        toJSON sets;

        buildCommand = ''

          touch $out

        '';