Update Swift CI, etc. for Xcode 10.2 beta 2

Apple's Swift repository still lists the original Xcode 10.2 beta. I already moved on to the second beta. Is the Swift compilation setup going to move there soon? Or is the code safe for either Xcode 10.2 beta?

Most likely that's just a reference to Xcode that hasn't been updated in the doumentation. Usually you can always use the latest beta of Xcode as far as I know.