anchor.diff:  
     buildInputs = [ pixman celt alsaLib openssl libjpeg zlib
                     libXrandr libXfixes libXrender libXext libXinerama
  -                  python pyparsing glib cyrus_sasl lz4 ];
  +                  python pyparsing glib cyrus_sasl libcacard lz4 ];
   
     nativeBuildInputs = [ pkgconfig spice-protocol ];
   
  
positive.code: 
    configureFlags = [
      "--with-sasl"
      "--disable-smartcard"
      "--enable-client"
      "--enable-lz4"
    ];
  
negative.code: { stdenv, fetchurl, pkgconfig, pixman, celt, alsaLib
  , openssl, libXrandr, libXfixes, libXext, libXrender, libXinerama
  , libjpeg, zlib, spice-protocol, python, pyparsing, glib, cyrus_sasl
  , libcacard, lz4 }:
  
  with stdenv.lib;
  
  