Fix bug #17104 - Target info for GNU/kFreeBSD were missing.
As a result, Clang doesn't define the pre-processor macros that are expected
on this platform.

Thanks to Robert Millan for the patch



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190048 91177308-0d34-0410-b5e6-96231b3b80d8