Edit in qmldir should trigger the CMake Generator

<Issue>
It seems to me that CMake Generator only runs when the root level .qmlproject file is edited, which means it doesn't run when a user edited a qmldir in a subdirectory. 

The use case I've just experienced is when I changed a QML component into singleton by modifying the qmldir in the subdirectory, the CMake didn't get updated, therefore, even thought the app ran on QDS, it didn't on Qt Creator.

<Suggestion>
Edit in qmldir should trigger the CMake Generator