We should be able to assume that a template instantiation or other COMDAT
has non-zero address even if MAKE_DECL_ONE_ONLY for the target sets
DECL_WEAK and we haven't yet decided to emit a definition in this
translation unit.

	PR c++/92003
	* symtab.c (symtab_node::nonzero_address): A DECL_COMDAT decl has
	non-zero address even if weak and not yet defined.