Allow building R backend with MSVC
While working on the r-base craft blueprint (packaging/craft-blueprints-kde!405 (merged)), I noted, you disable compilation of the R backend with MSVC, explicitly. I thought you may be interested in copying the method we use for RKWard. I did not actually test in your sources, but that is roughly the way, and works great for us.
If there's interest in enabling Mac support, that's in our sources, too, BTW.
Somewhat related, it would be great, if we could re-sync our FindR.cmake...