All end up with the task failing with a message along these lines:

[I 2018-02-12 03:14:26] About to install Xcode 9c40b in Xcode.app for ios
dyld: Library not loaded: /System/Library/Frameworks/Quartz.framework/Versions/A/Frameworks/PDFKit.framework/Versions/A/PDFKit
  Referenced from: /System/Library/Frameworks/Quartz.framework/Versions/A/Quartz
  Reason: image not found
dyld: Library not loaded: /System/Library/Frameworks/Quartz.framework/Versions/A/Frameworks/PDFKit.framework/Versions/A/PDFKit
  Referenced from: /System/Library/Frameworks/Quartz.framework/Versions/A/Quartz
  Reason: image not found
xcrun: error: unable to locate xcodebuild, please make sure the path to the Xcode folder is set correctly!
xcrun: error: You can set the path to the Xcode folder using /usr/bin/xcode-select -switch
iossim: ERROR: Unable to find a device iPhone 6s Plus with SDK 10.0.

iOS devices:

runtimes:
Using Xcode version None build None at None
Traceback (most recent call last):
  File "src/ios/build/bots/scripts/run.py", line 228, in <module>
    sys.exit(main())
  File "src/ios/build/bots/scripts/run.py", line 73, in main
    return 0 if tr.launch() else 1
  File "/b/s/w/ir/src/ios/build/bots/scripts/test_runner.py", line 409, in launch
    self.set_up()
  File "/b/s/w/ir/src/ios/build/bots/scripts/test_runner.py", line 608, in set_up
    self.wipe_simulator()
  File "/b/s/w/ir/src/ios/build/bots/scripts/test_runner.py", line 593, in wipe_simulator
    '-w',
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/b/s/w/ir/src/out/Debug-iphonesimulator/iossim', '-d', 'iPhone 6s Plus', '-s', '10.0', '-w']' returned non-zero exit status 2