[PATCH] Make compiler-rt tests work with relocatable SDKs on OS X

[Kuba Brecka]

>>! In D4047#11, @glider wrote:
> I've recently deinstalled LLVM from our Mavericks machine and am seeing the same problem now.
> But I'm not convinced it's a good idea to make all these symlink changes in compiler-rt CMake files. Instead this should probably be done in Clang.

Yeah, the automatic symlink creation is weird. How about just having a detection that there are c++ headers available, if not then we'll just stop building/testing informing you to either copy or symlink libcxx into your build directory.

For the SDKROOT stuff I still think we should detect and set this automatically, mostly because other parts of LLVM/Clang are doing it already.

http://reviews.llvm.org/D4047