[PATCH] Don't build tests for compiler-rt libs that aren't supported

[Reid Kleckner]

On Windows, only ASan is built.  However, we add the test suites for profile, tsan, and msan, all of which reference non-existing targets.  This prevents us from doing that.  If you want to hoist the logic for these decisions out of lib/CMakeLists, go for it, I'll close this.

http://reviews.llvm.org/D4709