opencv3 fails to provide legacy module in contrib variant, which is required by digikam port

[barracuda156]

digikam expects opencv to have legacy module in contrib, but our port (3.4.16_19) do not build it at all:

-- First try at finding OpenCV...
-- Could NOT find OpenCV (missing: contrib legacy) (found version "3.4.16")
CMake Warning at core/cmake/modules/MacroOpenCV.cmake:27 (find_package):
  Found package configuration file:

    /opt/local/libexec/opencv3/cmake/OpenCVConfig.cmake

  but it set OpenCV_FOUND to FALSE so package "OpenCV" is considered to be
  NOT FOUND.

This makes it impossible to build. And unfortunately, opencv is a hard dependency (getting rid of it looks feasible but involving).

[ryandesign (Ryan Carsten Schmidt)]

The digikam port already sets known_fail yes so it is known that it does not build.

It's also years out of date. This problem may already have been fixed in the latest version. See #62755.

[barracuda156]

Replying to ryandesign:

The digikam port already sets known_fail yes so it is known that it does not build.

It's also years out of date. This problem may already have been fixed in the latest version. See #62755.

Thank you. I have found what was going wrong for me: I needed -DENABLE_OPENCV3:BOOL=ON to make it use opencv3 correctly.

Updating it beyond 4.14.0 will not work for me, since it is the last version to support Qt4, but I am trying to build that one, of course, not our archaic portfile.