Update master to build with Xcode 10 beta 1, OS X 10.14, iOS 12, tvOS 12, and watchOS 5 SDKs.
Update master to build with Xcode 10 beta 1, OS X 10.14, iOS 12, tvOS 12, and watchOS 5 SDKs.

apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation