anchor.diff:        in
           with import "${nixos}/lib/testing.nix" {inherit nixpkgs services; system = "i686-linux";} ;
           runInMachineWithX {
  -          drv = pkgs.lib.overrideDerivation (build {}) (oldAttrs: { configureFlags = ""; buildInputs = oldAttrs.buildInputs ++ [pkgs.firefox] ; }) ;
  +          drv = pkgs.lib.overrideDerivation (build { inherit tarball; }) (oldAttrs: { configureFlags = ""; buildInputs = oldAttrs.buildInputs ++ [pkgs.firefox] ; }) ;
           };
   
     };
  
positive.code: 
    jobs = rec {
  
      tarball =
        with pkgs;
        releaseTools.makeSourceTarball {
          name = "webdsl-tarball";
  
negative.code:           pkgconfig 
          ] ++ strPkgs pkgs 
            ++ lib.optional stdenv.isLinux apacheAnt
            ++ lib.optional stdenv.isDarwin antDarwinNative
            ;
  
          configureFlags = "--enable-web-check=no";
  