anchor.diff:  , bzip2, flac, speex, icu, libopus
   , libevent, expat, libjpeg, snappy
   , libpng, libxml2, libxslt, v8
  -, xdg_utils, yasm, zlib
  +, xdg_utils, yasm, zlib, libwebp
   , libusb1, libexif, pciutils
   
   , python, pythonPackages, perl, pkgconfig
  
positive.code:     bzip2 flac speex icu libopus
      libevent expat libjpeg snappy
      libpng libxml2 libxslt v8
      xdg_utils yasm zlib
      libusb1 libexif
    ];
  
  
negative.code:     use_system_libexif = true;
      use_system_libjpeg = true;
      use_system_libpng = false; # PNG dlopen() version conflict
      use_system_libwebp = true;
      use_system_libxml = true;
      use_system_opus = true;
      use_system_snappy = true;
  