anchor.diff:  
     src =  fetchurl {
       url = "ftp://ftp.freedesktop.org/pub/mesa/${version}/MesaLib-${version}.tar.bz2";
  -    sha256 = "0gbacnnacv4x8q27s8my4qhf2xq8q4nyhbs9y9688win4csm12n7";
  +    sha256 = "0p8p35bwvrifc3v4z4wplxrs49h2qwzhcpsfjkkinfckkw6lqvg0";
     };
   
     prePatch = "patchShebangs .";
  
positive.code: */
  
  let
    version = "9.2.2";
    # this is the default search path for DRI drivers (note: X server introduces an overriding env var)
    driverLink = "/run/opengl-driver" + stdenv.lib.optionalString stdenv.isi686 "-32";
  in
  
negative.code:     "--enable-gallium-llvm" "--with-llvm-shared-libs"
      "--enable-xa" # used in vmware driver
      "--enable-gles1" "--enable-gles2"
      "--enable-vdpau"
  
      "--with-dri-drivers=i965,r200,radeon"
      ("--with-gallium-drivers=i915,nouveau,r300,r600,svga,swrast"
  