anchor.diff:  
         fetchurlBoot = fetchurl;
   
  -      inherit system shell gcc;
  +      inherit system shell gcc overrides;
       };
   
   
  
positive.code:   # A function that builds a "native" stdenv (one that uses tools in
    # /usr etc.).  
    makeStdenv =
      {gcc, fetchurl, extraPath ? []}:
  
      import ../generic {
        name = "stdenv-native";
  
negative.code:   };
  
  
    # Using that, build a stdenv that adds the ‘xz’ command (which most
    # systems don't have, so we mustn't rely on the native environment
    # providing it).
    stdenvBoot2 = makeStdenv {
      inherit gcc fetchurl;
      extraPath = [ stdenvBoot1Pkgs.xz ];
      overrides = pkgs: { inherit (stdenvBoot1Pkgs) xz; };
    };
  
  
  