anchor.diff:  { stdenv, fetchurl, flex, bison, pkgconfig, x11, xlibs, libdrm, file, expat
  -, pythonFull, lipo ? null, talloc }:
  +, python, libxml2Python, lipo ? null }:
   
   if ! stdenv.lib.lists.elem stdenv.system stdenv.lib.platforms.mesaPlatforms then
     throw "unsupported platform for Mesa"
  
positive.code:   buildInputs =
      [ pkgconfig expat x11 libdrm xlibs.makedepend xlibs.glproto
        xlibs.libXxf86vm xlibs.libXfixes xlibs.libXdamage xlibs.dri2proto
        lipo talloc file pythonFull flex bison
      ];
  
    enableParallelBuilding = true;
  
negative.code:   patches = [ ./swrast-settexbuffer.patch ];
  
    postPatch = ''
      find . -name "*.py" -exec sed -i -e "s|#! */usr/bin/env python|#! ${python}/bin/python|" {} +
    '';
  
    configureFlags =
  