graphics/ImageMagick[6-7]: optionize the dependency on ffmpeg
- Make an option for FFMPEG, and do not enable it by default.
- Do not bump PORTREVISION: pkg will take care of it, and ports users may rebuild it if needed.
- Note: there is no simple way to deactivate this option when ffmpeg is already installed.
PR: 256215
Reported by: Toshimichi Masubuchi (ImageMagick7) and gessel (6)
Approved by: maintainer’s time-out