anchor.diff:  
       allowedRequisites =
         [ bootstrapTools ] ++
  -      (with pkgs; [ xz.bin xz.out libcxx libcxxabi icu.out ]) ++
  -      (with pkgs.darwin; [ dyld Libsystem CF locale ]);
  +      (with pkgs; [ xz.bin xz.out libcxx libcxxabi ]) ++
  +      (with pkgs.darwin; [ dyld Libsystem CF ICU locale ]);
   
       overrides = persistent1 prevStage;
     };
  
positive.code:   persistent4 = prevStage: self: super: with prevStage; {
      inherit
        gnumake gzip gnused bzip2 gawk ed xz patch bash
        libcxxabi libcxx ncurses libffi zlib icu llvm gmp pcre gnugrep
        coreutils findutils diffutils patchutils;
  
      llvmPackages = super.llvmPackages // {
  
negative.code: 
      allowedRequisites =
        [ bootstrapTools ] ++
        (with pkgs; [ xz.bin xz.out bash libcxx libcxxabi ]) ++
        (with pkgs.darwin; [ dyld ICU Libsystem locale ]);
  
      overrides = persistent2 prevStage;
    };
  