QtIFW

Fix broken build on Mac

On Mac the variable "scTargetDir" was not defined. This block of code
was behind "#ifdef Q_OS_MAC" so other platforms were not affected.

Added constants.h include for mac only to resolve the missing
global constant.

Change-Id: Ia8bef78d7c3015f283b202435d56d00187f3fb4f
Reviewed-by: Tim Jenssen <tim.jenssen@nokia.com>