anchor.diff:      buildInputs =
         [ pkgconfig gtk perl zip libIDL libjpeg zlib cairo bzip2 python
           dbus dbus_glib pango freetype fontconfig alsaLib nspr libnotify
  -        xlibs.pixman libvpx yasm
  +        xlibs.pixman libvpx yasm mesa
         ];
   
       propagatedBuildInputs = [xulrunner];
  
positive.code:       [ pkgconfig gtk perl zip libIDL libjpeg libpng zlib cairo bzip2
          python dbus dbus_glib pango freetype fontconfig xlibs.libXi
          xlibs.libX11 xlibs.libXrender xlibs.libXft xlibs.libXt file
          alsaLib nspr /* nss */ libnotify xlibs.pixman libvpx yasm
        ];
  
      configureFlags =
  
negative.code: { stdenv, fetchurl, pkgconfig, gtk, pango, perl, python, zip, libIDL
  , libjpeg, libpng, zlib, cairo, dbus, dbus_glib, bzip2, xlibs
  , freetype, fontconfig, file, alsaLib, nspr, nss, libnotify
  , libvpx, yasm, mesa
  
  , # If you want the resulting program to call itself "Firefox" instead
    # of "Shiretoko" or whatever, enable this option.  However, those
  