anchor.diff:        "ftp://ftp.freedesktop.org/pub/mesa/older-versions/${branch}.x/${version}/mesa-${version}.tar.xz"
         "https://mesa.freedesktop.org/archive/mesa-${version}.tar.xz"
       ];
  -    sha256 = "0pq9kmmyllgd63d936f3x1zsg7sqaswx47khbn0gvbgari2h753f";
  +    sha256 = "16rpm4rwmzd4kdgipa1gw262jqg3346gih0y3bsc3bgn1vgcbfj1";
     };
   
     prePatch = "patchShebangs .";
  
positive.code: in
  
  let
    version = "17.2.8";
    branch  = head (splitString "." version);
    driverLink = "/run/opengl-driver" + optionalString stdenv.isi686 "-32";
  in
  
negative.code:     "--enable-shared-glapi"
      "--enable-sysfs"
      "--enable-llvm-shared-libs"
      "--enable-omx-bellagio"
      "--enable-va"
      "--disable-opencl"
    ];
  