Squish: Fix accessing Options on OSX

Accessing the application menu inside the menubar of OSX
does not work properly since using Qt5.
For some time using default keysequences worked fine, but
for the Preferences (Options menu) this stopped working,
so make the used hack even more crude.

Change-Id: I48ed37dc69b8c64f649f0130d48d4deb02afb87e
Reviewed-by: Robert Loehning <robert.loehning@qt.io>