Stabilize QFileSystemModel::dirsBeforeFiles test

Make the test operate in its own temporary directory, so that entries
left behind by other test functions don't impact this test.

Also, call QFileSystemModel::sort explicitly; it would otherwise only
be done once through a single-shot timer, and the test processes events
until the model is populated, which might not process that delayed
sorting. Since dirsBeforeFiles tests the sorting algorithm and not
the sorting logic, best to do this explicitly.

In case of sort failure, print diagnostics.

Change-Id: I44c2b82ef1330cc8787aed2b5cbf109ef3a67876
Done-with: Friedemann Kleint <Friedemann.Kleint@qt.io>
Fixes: QTBUG-75452
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

0 files changed, 0 insertions, 0 deletions