Switch to clang_rt.profile library for testing

`GCDAProfiling` was duplicated in both LLVM and compiler-rt.

The one in LLVM has been removed recently from its `profile_rt` library. This results in linking errors when build OCLint with unit testing.

So, we now switch to link against the one provided by compiler-rt. CMake build for compiler-rt's profile library was not supported for a while, and thanks to Alexey's effort, this is added recently.