ObjectiveC driver. Scrap -fno-objc-legacy-dispatch for NeXT
runtime. It will be silently ignored and regardless
of deployment target. // rdar://14803286


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192719 91177308-0d34-0410-b5e6-96231b3b80d8