iOS: Cannot start or deploy to simulator using Xcode 6

Steps to reproduce:

• open/create Qt Quick Application or Qt Widgets Application
• have an iOS kit configured (for simulator)
• build it

Current result:

• build succeeds, but fails to deploy
• Compile Output pane shows sth like this at the bottom:

  ** BUILD SUCCEEDED **
  
  13:40:55: The process "/usr/bin/make" exited normally.
  13:40:55: Application install on Simulator failed. Simulator not running.
  Error while building/deploying project untitled7 (kit: iphonesimulator-clang Qt 5.6.0 (qt56))
  The kit iphonesimulator-clang Qt 5.6.0 (qt56) has configuration issues which might be the root cause for this problem.
  When executing step "Deploy to iOS Simulator"
  13:40:55: Elapsed time: 00:53.
  

Note: inside the Run settings of the Device type combobox is completely empty, I'm not able to select any device.
Note2: the "configuration issues" mentioned inside the Compile Output pane is simply a warning regarding cmake stuff, so completely unrelated and definitely not the root cause.