anchor.diff:  , freetype, fontconfig, file, alsaLib, nspr, nss, libnotify
   , yasm, mesa, sqlite, unzip, makeWrapper, pysqlite
   , hunspell, libevent, libstartup_notification, libvpx
  -, cairo ? null
  -, useSystemCairo ? false
  +, cairo
   , # If you want the resulting program to call itself "Firefox" instead
     # of "Shiretoko" or whatever, enable this option.  However, those
     # binaries may not be distributed without permission from the
  
positive.code:       [ pkgconfig libpng gtk perl zip libIDL libjpeg zlib bzip2 python
          dbus dbus_glib pango freetype fontconfig alsaLib nspr nss libnotify
          xlibs.pixman yasm mesa sqlite file unzip pysqlite
          hunspell libevent libstartup_notification libvpx
        ] ++ optional useSystemCairo cairo;
  
      patches = [
        ./disable-reporter.patch # fixes "search box not working when built on xulrunner"
  
negative.code: }:
  
  assert stdenv.gcc ? libc && stdenv.gcc.libc != null;
  
  let optional = stdenv.lib.optional;
  in rec {
  