According to this issue there’s Xcode 10.2 support: Xcode 10.2 beta 3 Image Released
But it seems it is Xcode 10.2 beta, as I’m getting this error when trying to submit a build to TestFlight:
Invalid Toolchain. Your app was built with an unsupported version of Xcode or SDK. If you plan to submit this build to the App Store, make sure you are using the GM version of Xcode 9 and the SDK for iOS 11, tvOS 11, watchOS 4, or macOS 10.13 or later. If you are using an Xcode beta version to test your app, make sure you are using the latest supported version. For more information about supported beta versions, view the TestFlight Release Notes