CMake - _qmltyperegistration.cpp do not get updated

If I change classnames with QML_ELEMENT or remove/add QML_ELEMENT *_qmltyperegistration.cpp does not get updated.

I am not sure if this intended behaviour or not.

Reproduce with the attached example project:

1. Build it.
2. Check app_qmltyperegistrations.cpp or plugin/plugin_qmltyperegistrations.cpp
3. Uncomment QML_ELEMENT in AppType.h or plugin/PluginType.h
4. configure and/or Build again, *_qmltyperegistrations.cpp do not change
5. run clean
6. configure/build
7. *_qmltyperegistrations.cpp are updated now

PS: The example does not run, could not figure out why. Not important for the issue I hope.