anchor.diff:  , curl
   , dbus
   , expat
  -, faad2
   , ffmpeg
   , flac
   , fluidsynth
  
positive.code: 
    configureFlags = [
      "--help"
      "--${boolEn (faad2 != null)}-aac"
      # TODO: adplug support
      #"--${boolEn }-adplug" true null)
      "--${boolEn (alsa-lib != null)}-alsa"
  
negative.code:     curl
      dbus
      expat
      ffmpeg
      flac
      fluidsynth
  