clang-cl: Add /FS as an ignored flag

CMake-generated Makefiles include this cl flag which can be safely ignored
until we get PDB server support.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194165 91177308-0d34-0410-b5e6-96231b3b80d8
[build] Update runtime library and tests to work with relocatable SDKs on OS X 10.9.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194168 91177308-0d34-0410-b5e6-96231b3b80d8