anchor.diff:    buildInputs = [
       expat
       libffi
  +    libxml2
     ];
   
     configureFlags = [
  
positive.code: , libxslt
  , xmlto
  
  , libffi
  , expat
  
  , enableDocumentation ? false
  }:
  
negative.code: 
  stdenv.mkDerivation rec {
    name = "wayland-${version}";
    version = "1.10.0";
  
    src = fetchurl {
      url = "http://wayland.freedesktop.org/releases/${name}.tar.xz";
      sha256 = "1p307ly1yyqjnzn9dbv78yffql2qszn84qk74lwanl3gma8fgxjb";
    };
  
    nativeBuildInputs = [ ]
  