[Cin] Limit number of opencv modules we build

Hopefully I get them right! Builds with opencv4 (2020 tarball) on Slackware -current x86_64 hopefully will make compile farm's job a bit easier. Note, I only modded and tested local static build, you can try to add similar line (with closing "\" !) to second, dynamic case in opencv_build file in root of cingg source tree.