On Windows, having read-only files in a directory can cause removal
to fail. When file deletion fails, check on the permissions, set
write permissions and retry.
Split apart code paths by OS in tst_QDir::removeRecursivelyFailure();
deletion of the read-only directory on UNIX should still fail.
Change-Id: I36e54be5229a7b552e90fd5f42722b868fa0b6ee
Reviewed-by: David Faure <david.faure@kdab.com>
26bcc0565f