Qnx: Detect Qt version for BB10 with the new mkspec changes

Task-number: QTCREATORBUG-12222
Change-Id: I28cfc2a3d35f55576bd52ecb720d74c6d432786e
Reviewed-by: Sergio Ahumada <sahumada@blackberry.com>
Reviewed-by: Wolfgang Bremer <wbremer@blackberry.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>