Compile fix for Qt 5.9

This here is a trivial backport of 991f5eb6 which doesn't
apply cleanly due to renamings in that area.

It is meant to help regression testing Qt Creator over a wider
range of versions bridging the source compatibility breakage
in change 821390b7c3a9438 in Qt Core.

Change-Id: Ib6d06927dbe16f94b21caca0993f524b282f167a
Reviewed-by: Eike Ziller <eike.ziller@qt.io>