I added the CMakeLists.txt 6 or 7 years ago so I could load the code
into Jetbrains Clion. I have moved to another editor years ago and the
cmake stuff is effectively unmaintained since then. We kept it around
in case that we'll do a MSVC port, but that's unlikely at this point.
Since bugreport and problems with the CMakeLists.txt keep coming up,
finally retire them. They can be resurrected from the git history if
we'll ever need them again.
Part of yquake2/yquake2#725.