IRGen: Switch pass managers based on LegacyPassManager IRGenOptions flag
IRGen: Switch pass managers based on LegacyPassManager IRGenOptions flag

benlangmuir/swift,roambotics/swift,JGiola/swift,roambotics/swift,JGiola/swift,glessard/swift,apple/swift,benlangmuir/swift,JGiola/swift,JGiola/swift,glessard/swift,apple/swift,roambotics/swift,apple/swift,glessard/swift,glessard/swift,JGiola/swift,benlangmuir/swift,benlangmuir/swift,glessard/swift,JGiola/swift,apple/swift,benlangmuir/swift,roambotics/swift,glessard/swift,benlangmuir/swift,roambotics/swift,roambotics/swift,apple/swift,apple/swift