The recent addition of regression tests to uuid-ossp exposed the fact
that the MSVC build system wasn't being consistent about whether it was
building/testing that contrib module, ie, it would try to test the module
even when it hadn't built it.  The same hazard was latent for sslinfo.

For the moment I just copied the more up-to-date logic from point A to
point B, but this is screaming for refactoring.

Per buildfarm results.