[llvm] r309310 - Un-revert "Teach the CMake build system to run lit's test suite. These can be run"

[Brian Gesiak via llvm-commits]

Marking `lit :: shtest.py` as `UNSUPPORTED: windows` would prevent it
from being run on Windows, at least until we can fix the error. But
ideally we'd have some way to reproduce it locally, otherwise it's
just a matter of time before someone re-enables the test and causes
the same buildbot failure again.

- Brian Gesiak