anchor.diff:      url = "mirror://mozilla/firefox/releases/${version}esr/source/firefox-${version}esr.source.tar.xz";
       sha256 = "1mlx34fgh1kaqamrkl5isf0npch3mm6s4lz3jsjb7hakiijhj7f0";
     };
  +
  +  outputs = [ "out" "dev" ];
  +  setOutputFlags = false; # Configure script only understands --includedir
   
     buildInputs = [ readline icu zlib nspr ];
     nativeBuildInputs = [ autoconf213 pkgconfig perl which python2 zip ];
  
positive.code:     export CXXFLAGS="-fpermissive"
      export LIBXUL_DIST=$out
      export PYTHON="${python2.interpreter}"
  
      cd js/src
  
  
negative.code: 
    enableParallelBuilding = true;
  
    postInstall = ''
      moveToOutput bin/js52-config "$dev"
      # Nuke a static lib.
      rm $out/lib/libjs_static.ajs
    '';
  
    meta = with stdenv.lib; {
      description = "Mozilla's JavaScript engine written in C/C++";
      homepage = https://developer.mozilla.org/en/SpiderMonkey;
  