swift

90b8e13f - Run ObjCARCContract when optimizing no matter the IRGenOutputKind.

Run ObjCARCContract when optimizing no matter the IRGenOutputKind. Previously, we were just running ObjCARCContract when codegening. This is out of character with the rest of the LLVM passes in Swift, namely that after these have run, an IR pass no longer contains any compiler intrinsics. This can be seen by SwiftARCContract running in the -O pipeline. This commit harmonizes the behavior here. For testing purposes, I added a flag that disables the running of ObjCARCContract for testing purposes. rdar://34824507 (cherry picked from commit 723c6212f2b7e7f0f620a68b57bad9f2386e3c9d)