[MacPorts] #70729: opencv4 doesn't work with ffmpeg or ffmpeg7

[MacPorts]

#70729: opencv4 doesn't work with ffmpeg or ffmpeg7
-------------------------+---------------------
 Reporter:  Lord-Kamina  |      Owner:  (none)
     Type:  defect       |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:  2.10.1
 Keywords:               |       Port:  opencv4
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 OpenCV4 has the following dependency `path:lib/libavcodec.dylib:ffmpeg`.
 This means if ffmpeg 6 or 7 are installed, it will insist on installing
 ffmpeg 4.4 and linking itself against that.

 Symlinking the correct library from `libexec/ffmpeg at version@/lib` onto the
 main `lib` folder works fine, but is of course very cumbersome and
 unintuitive.

 I'm not sure what the best way to to go around fixing this is. I'm
 thinking of two possibilities:

 1) Variants.
 2) Adding the folders inside libexec to the paths macports searches to
 satisfy this kind of dependencies.

 I think conceptually, the ideal would be the latter but I'm not sure
 whether that's at all possible, and/or whether it could be done without
 adding uncertainty to builds in cases where more than one version of
 ffmpeg is installed at once, so maybe it'd be safer to go with variants.

 Not sure what anyone else thinks about this?

-- 
Ticket URL: <https://trac.macports.org/ticket/70729>
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