QNX: Add qt.conf file

This will enable us to use the qt5_essentials.7z build package
outside of the installers as well, just like a standalone build.

Change-Id: Ibb908591fc6110a812a0e3b871024f626aa322de
Reviewed-by: Wolfgang Bremer <wbremer@blackberry.com>
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>