Add missing GENERATE_PLUGIN_SOURCE to merkuro_contact_plugin
Launching merkuro-calendar
from v24.08.0 was failing with:
QQmlApplicationEngine failed to load component
qrc:/main.qml:328:19: Type MainDrawer unavailable
qrc:/MainDrawer.qml:341:9: Type CheckableCollectionNavigationView unavailable
qrc:/CheckableCollectionNavigationView.qml:11:1: Failed to extract plugin meta data from '/usr/lib/qt6/qml/org/kde/merkuro/contact/libmerkuro_contact_pluginplugin.so': '/usr/lib/qt6/qml/org/kde/merkuro/contact/libmerkuro_contact_pluginplugin.so' is not a Qt plugin (metadata not found)
As seen downstream in https://github.com/chimera-linux/cports/pull/2772