pkgs.useMoldLinker

The following is the current implementation of this function.

stdenv:
    if stdenv.targetPlatform.isDarwin then
      throw "Mold can't be used to emit Mach-O (Darwin) binaries"
    else
      let
        bintools = stdenv.cc.bintools.override {
          extraBuildCommands = ''
            pushd $out/bin
            ln -s ${pkgs.buildPackages.mold}/bin/${stdenv.cc.bintools.targetPrefix}ld.mold ${stdenv.cc.bintools.targetPrefix}ld.mold
          '' # Pre-generated configure scripts call the linker binary without the target prefix when cross compiling.
          + lib.optionalString (stdenv.cc.bintools.targetPrefix != "") ''
            ln -s ${stdenv.cc.bintools.targetPrefix}ld.mold ld.mold
          ''
          + ''
            popd
          '';
        };
      in
      stdenv.override (
        old:
        {
          allowedRequisites = null;
          cc = stdenv.cc.override { inherit bintools; };
          # gcc >12.1.0 supports '-fuse-ld=mold'
          # the wrap ld above in bintools supports gcc <12.1.0 and shouldn't harm >12.1.0
          # https://github.com/rui314/mold#how-to-use
        }
        //
          lib.optionalAttrs
            (stdenv.cc.isClang || (stdenv.cc.isGNU && lib.versionAtLeast stdenv.cc.version "12"))
            {
              mkDerivationFromStdenv = extendMkDerivationArgs old (args: {
                env = (args.env or { }) // {
                  NIX_CFLAGS_LINK = toString (args.env.NIX_CFLAGS_LINK or "") + " -fuse-ld=mold";
                };
              });
            }
      )