Check xcode-select is set
Check xcode-select is set

Summary:
Basic check for some xcode-path

There'll be a separate connected device check that looks at the current simulators and sees if they are running the same xcode version.

Reviewed By: mweststrate

Differential Revision: D18427090

fbshipit-source-id: 5e202d8920cae1ffce444e81a0c138a97936f758

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper