Fixing Info.plist.in for qmlobserver and qmldump

Since we use Info.plist.in we need QMAKE_SUBSTITUTES
and cannot use QMAKE_INFO_PLIST.
We manualy replicate the target logic.

Change-Id: I5b703d09db85457ba3bdadef97fd1cc2194b618f
Reviewed-by: Eike Ziller <eike.ziller@digia.com>