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