http://bugs.winehq.org/show_bug.cgi?id=26862
--- Comment #7 from Jerome Leclanche adys.wh@gmail.com 2011-04-21 03:27:26 CDT --- (In reply to comment #6)
That's not a debugger, but rather corefile catcher. And it's working only when game is running under Steam, which is not this case (bug #26835)
Try wine portal2.exe -novid -nobreakpad -nominidumps