(rule
 (target ffmpeg.config)
 (mode
  (promote
   (only ffmpeg.config)
   (until-clean)))
 (action
  (progn
   (echo "ffmpeg library availability:\n")
   (echo "  avutil:     %{read:detect/avutil_available}\n")
   (echo "  avcodec:    %{read:detect/avcodec_available}\n")
   (echo "  avfilter:   %{read:detect/avfilter_available}\n")
   (echo "  avdevice:   %{read:detect/avdevice_available}\n")
   (echo "  av:         %{read:detect/av_available}\n")
   (echo "  swscale:    %{read:detect/swscale_available}\n")
   (echo "  swresample: %{read:detect/swresample_available}\n")
   (with-stdout-to
    %{target}
    (echo "")))))
