[objcmt] Don't wrap a PCH generation action with a ObjCMigrateAction one, it messes up the PCH file.

rdar://16941811

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@209059 91177308-0d34-0410-b5e6-96231b3b80d8
More fixes for isBetterOverloadCandidate not being a strict weak ordering. The
bug was obvious from inspection, figuring out a way to test it was... less so.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@209060 91177308-0d34-0410-b5e6-96231b3b80d8