With an openglcompositor, only first QEglFSWindow is set
with a flag, HasNativeWindow and when it is destroyed,
the openglcompositor is destroyed, too.
For now, when using openglcompositor, Qt will not check
HasNativeWindow for its nativeWindow because it is not
possible to add a HasNativeWindow flag in an existing
window. And the openglcompositor will be destroyed after
the all the QEglFSWindows are closed.
Fixes: QTBUG-129576
Pick-to: 6.8 6.5
Change-Id: I620a904a03d29e8db1738d9392f716b3ebf5b553
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>