anchor.diff:            cc = gccPlain;
             isGNU = true;
             libc = glibc;
  -          inherit binutils coreutils;
  +          inherit binutils coreutils gnugrep;
             name = name;
             stdenv = stage0.stdenv;
           };
  
positive.code:   # Construct a fourth stdenv that uses the new GCC.  But coreutils is
    # still from the bootstrap tools.
    stage4 = stageFun {
      inherit (stage3.pkgs) gccPlain glibc binutils;
      coreutils = bootstrapTools;
      name = "";
  
  
negative.code:     inherit (stage1.pkgs) glibc;
      binutils = stage1.pkgs.binutils;
      coreutils = bootstrapTools;
      gnugrep = bootstrapTools;
      name = "bootstrap-gcc-wrapper";
  
      overrides = pkgs: {
  