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

[Alexander Potapenko]

> 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.
Can't this be done by installing the Xcode command line tools? (I've failed to, but perhaps I was doing something wrong)
 
> 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.
Any pointers? A quick grep doesn't show any additional -isysroot flags.

================
Comment at: compiler-rt/trunk/cmake/Modules/AddCompilerRT.cmake:151
@@ +150,3 @@
+  list(APPEND COMPILER_RT_GTEST_CFLAGS -isysroot ${OSX_SDK_DIR})
+  list(APPEND ASAN_UNITTEST_COMMON_LINKFLAGS -isysroot ${OSX_SDK_DIR})
+  list(APPEND ASAN_UNITTEST_COMMON_LINKFLAGS -framework Foundation)
----------------
I think ASAN_UNITTEST_COMMON_LINKFLAGS should be set in the corresponding build config.

http://reviews.llvm.org/D4047