When accidentally pressing 'Debug' on a library project,
the dialog asking for the executable pops up and debugging still
starts although cancel is pressed.

Add dialog title, set flags, and check its return values.

Change-Id: I8518b8af70b12a7059f9ee0e20a9d0b325db1e98
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>