Xcode 10.1 support

[marc]

We have just done the release:

Xcode 10.1 Image Released

We have released an Xcode 10.1 macOS image today. You can select the image by adding the following to a job in config.yml: macos: xcode: 10.1.0 The changes in this image since the Xcode 10 image are: Xcode is now version 10.1 Build 10B61. The Command Line Tools are now version 10.1. We have upgraded to the latest macOS High Sierra 10.13.6 (17G3025). We have removed the simulators for WatchOS 4.2. See the note below. The available Apple Watch simulators are: Series 2 - 38mm (5.1) Series 2…