anchor.diff:      libX11 libXext libxcb libXt libXfixes libxshmfence
       libffi wayland wayland-protocols libvdpau libelf libXvMC
       libomxil-bellagio libva-minimal libpthreadstubs openssl/*or another sha1 provider*/
  -    valgrind-light python2
  +    valgrind-light python2 python27Packages.Mako
     ];
   
     enableParallelBuilding = true;
  
positive.code: in
  
  let
    version = "18.0.3";
    branch  = head (splitString "." version);
  in
  
  
negative.code:       "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 = "1ydivzm4c2k53b65lvm11d62z140xlmd7viw63bl5cm5idjg02q7";
    };
  
    prePatch = "patchShebangs .";
  