anchor.diff:      ++ optional aacSupport faad2
       ++ optional opusSupport opusfile
       ++ optional zipSupport libzip
  -    ++ optional ffmpegSupport ffmpeg_3
  +    ++ optional ffmpegSupport ffmpeg
       ++ optional apeSupport yasm
       ++ optional artworkSupport imlib2
       ++ optional hotkeysSupport libX11
  
positive.code: , aacSupport ? true, faad2 ? null
  , opusSupport ? true, opusfile ? null
  , wavpackSupport ? false, wavpack ? null
  , ffmpegSupport ? false, ffmpeg_3 ? null
  , apeSupport ? true, yasm ? null
  # misc plugins
  , zipSupport ? true, libzip ? null
  
negative.code: assert aacSupport -> faad2 != null;
  assert opusSupport -> opusfile != null;
  assert zipSupport -> libzip != null;
  assert ffmpegSupport -> ffmpeg != null;
  assert apeSupport -> yasm != null;
  assert artworkSupport -> imlib2 != null;
  assert hotkeysSupport -> libX11 != null;
  