After the update of graphics/opencv to version 4.5.1 graphics/frei0r-plugins-opencv
does not build anymore.
It turns out, that there have some important fixes to graphics/frei0r [1] after the
the release of v1.7.0 [1].
[1] https://github.com/dyne/frei0r/compare/v1.7.0...master
This patch updates the port to v1.7.0-18. The metaport and all its subports now
build again.