But the dependency is hidden behind dynamic loading in plugin.cpp;
so for qmlimportscanner to know about it, we have to declare it,
and qmlimportscanner needs to react to the "depends" line in qmldir.

Task-number: QTBUG-41489
Change-Id: I739791e07a72d628f8c08d067566631c59c7375e
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>