anchor.diff:  
     src =  fetchurl {
       url = "ftp://ftp.freedesktop.org/pub/mesa/${version}/MesaLib-${version}.tar.bz2";
  -    sha256 = "1g2vy7zaamzs00xasiwg0d6cb5sclfd9v8jms14ll9bghg3mwv5w";
  +    sha256 = "171rfxa5i4rhc373h0his60lji7v7iplysd1vb6qj3q0ch1s9i1q";
     };
   
     prePatch = "patchShebangs .";
  
positive.code: */
  
  let
    version = "10.1.5";
    # this is the default search path for DRI drivers
    driverLink = "/run/opengl-driver" + stdenv.lib.optionalString stdenv.isi686 "-32";
  in
  
negative.code:     "--enable-glx-tls"
      "--enable-shared-glapi" "--enable-shared-gallium"
      "--enable-driglx-direct" # seems enabled anyway
      "--enable-gallium-llvm" "--enable-llvm-shared-libs"
      "--enable-xa" # used in vmware driver
      "--enable-gles1" "--enable-gles2"
      "--enable-vdpau"
  