Only show the "Do you want to recompile now?" modal dialog if the
"Enable QML debugging" or "Enable Qt Quick Compiler" checkboxes have
been changed directly by the user.

The previous change let the QML debugging checkbox update also when the
.pro file has changed. Showing a modal dialog in such cases interrupts
the user's flow, and is unexpected.

Change-Id: I9304cbecee7e201694ff72ac8c0f38cedf5fb416
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>