ffmpeg: add rubberband and zimg options.
ffmpeg: add rubberband and zimg options.

Both are external libraries supported since FFmpeg 3.0.

Closes #49411.

Signed-off-by: Mike McQuaid <a17fed27eaa842282862ff7c1b9c8395a26ac320@mikemcquaid.com>

filcab/homebrew,filcab/homebrew,filcab/homebrew,filcab/homebrew