qml tool fails to load scenes where root is not Window or Item

Typically, in a Qt Wayland Compositor, the root object will be a WaylandCompositor and the Window will be created per WaylandOutput. In the "qml" tool, it requires that the root object of the scene is a Window, otherwise it exits early. This is inconsistent with the behavior of "qmlscene".

For an example, the minimal-qml example in Qt Wayland can be used.

Run "qml main.qml" and it prints out "Did not load any objects" before exiting. Run "qmlscene main.qml" and it runs fine.