Regression: "Could not connect to the in-process QML debugger" with Qt 4.7

1. Create a new Qt Quick 1 Application (Built-in Types) and configure it with a kit using Qt 4.7.
2. Go to Projects mode, Build settings for this kit.
3. In "Build Steps", "qmake", check "Enable QML debugging". If needed, click the "Compile..." link first.
4. Build the project and start debugging it.
   A message box will appear:
   

This used to work with Creator 2.8. In 3.0, it works with Qt 4.8 and 5.0.

Found by Squish test tst_simple_debug.