Debugger: Startup fixes for LLDB

On Mac, don't ignore the 'attach' stop, as it causes trouble
in the Terminal case. So a terminal start needs extra
'continues' but doesn't crash LLDB anymore.

Change-Id: Iaa72e3f5cfc02d8cd1841fa57e0633109645da31
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>