Fix profiledbootstrap

Fix profiledbootstrap

Profiledbootstrap fails with ICE in update_loop_exit_probability_scale_dom_bbs
called from loop unroling.
The reason is that under relatively rare situations, we may run into case where
loop has multiple exits and all are considered as likely but then we scale down
the profile and one of the exits becomes unlikely.

We pass around unadjusted_exit_count to scale exit probability correctly.  In this
case we may end up using uninitialized value and profile-count type intentionally
bombs on that.

gcc/ChangeLog:

	PR bootstrap/110857
	* cfgloopmanip.cc (scale_loop_profile): (Un)initialize
	unadjusted_exit_count.