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

[Brian Gesiak via llvm-commits]

Victor, Douglas,

I've verified https://reviews.llvm.org/D36212 fixes the issue for me;
builds on my macOS and Windows hosts succeed. Please take a look and
let me know if it fixes the issues on your buildbot.

Thanks for your help debugging, and your patience!

- Brian