Resuming work on the compiler-rt CMake build at long long last. In order

to get it working again, two changes were needed:

- I had to give up on glob-based file expansion. This just isn't well
  supported by CMake, and until we convince upstream there of its value,
  it's not worth dealing with the pain.
- Add the common library as otherwise even ASan won't build.

This now builds again, although the "correctness" of it is a touch
debatable. ;] Specifically, there is no merging of the common runtime
library with the asan runtime library into a single archive file. I'm
not really sure what the best technique is for that, and it may be
influenced by the ongoing discussion about how best to link runtime
libraries.

Note of course that this is still very much WIP. It doesn't entirely
work yet, and remains disabled by the LLVM projects/CMakeLists.txt until
it is in a working state.

llvm-svn: 158811