re PR target/63892 (gcc.dg/sibcall-3.c fails on darwin with -m32)

re PR target/63892 (gcc.dg/sibcall-3.c fails on darwin with -m32)

	PR target/63892
	* ipa-icf.c (sem_function::merge): If DECL_COMDAT_GROUP (alias->decl),
	don't try to create_thunk if stdarg_p.  If
	!sem_item::target_supports_symbol_aliases_p (), similarly, and try to
	redirect_callers if possible.
	(sem_item_optimizer::execute): Call unregister_hooks here...
	(ipa_icf_driver): ... instead of here.

Co-Authored-By: Martin Liska <mliska@suse.cz>
From-SVN: r220875