QGtk3ThemePlugin: includemocs

Including moc files directly into their classes' TU tends to improve
codegen and enables extended compiler warnings, e.g. about unused
private functions or fields.

Pick-to: 6.3 6.2 5.15
Task-number: QTBUG-102886
Change-Id: I1e023a23a95088effbbcd830eff627fbc4a3c12a
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/plugins/platformthemes/gtk3/qgtk3dialoghelpers.cpp

@@ -664,4 +664,6 @@ void QGtk3FontDialogHelper::applyOptions()
 
 QT_END_NAMESPACE
 
+#include "moc_qgtk3dialoghelpers.cpp"
+
 #include "qgtk3dialoghelpers.moc"

src/plugins/platformthemes/gtk3/qgtk3menu.cpp

@@ -483,3 +483,5 @@ void QGtk3Menu::onHide(GtkWidget *, void *data)
 }
 
 QT_END_NAMESPACE
+
+#include "moc_qgtk3menu.cpp"