The version numbers of the darwin kernel are different from the version
numbers of OS X, so we need adjustments if we had "*-*-darwin" triples.
Use the existing utility functions in TargetTriple for this.
Fixes rdar://22056966
Differential Revision: http://reviews.llvm.org/D14601
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257555 91177308-0d34-0410-b5e6-96231b3b80d8