Annotate empty bb with all debug_stmt with location of phi in the single_succ.

Annotate empty bb with all debug_stmt with location of phi in the single_succ.

For an empty BB with all debug_stmt, it will be ignored by
afdo_set_bb_count, but it can be set with count of single successors
PHIs which edge from the BB.

gcc/ChangeLog:

	PR gcov-profile/118581
	* auto-profile.cc (autofdo_source_profile::get_count_info):
	Overload the function with parameter gimple location instead
	of stmt.
	(afdo_set_bb_count): For !has_annotated BB, Check single
	successors PHIs corresponding to the block and use those
	count.