Revert 189756 for now, it doesn't match what rdar://14871821 really wants.

What we really want is to enable Swift by default for *v7s triples (and there already seems to be some logic which attempts to do that). In that case the iOS version doesn't matter. 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189763 91177308-0d34-0410-b5e6-96231b3b80d8