Qt DBus recently became a dependency for the platform plugin,
causing applications to crash on startup when this is missing.
Instead of special casing the GUI dependency, we always add all
dependencies of the platform plugin.

Change-Id: I59d71531f60874ce436af1840656974d58c14661
Task-number: QTBUG-44182
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>