This adds dependencies on private Qt headers for the QNX plugin, as
we need the QZipReader to read the .bar file.

Change-Id: Id70def551776a9d5ac43203cf807d2a0ca65e22f
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>