Driver: honour the clang-cl behaviour on ARM as well

Unfortunately, MSVC does not indicate to the driver what target is being used.
This means that we cannot correctly select the target architecture for the
clang_rt component.  This breaks down when targeting windows with the clang
driver as opposed to the clang-cl driver.  This should fix the native ARM
buildbot tests.

llvm-svn: 225089
1 file changed