PR c++/92774 - ICE with implicitly deleted operator<=>.

Missing error-recovery code.  While I was poking at this I also figured we
don't need to iterate over the members of a union.

	* method.c (comp_info::~comp_info): Factor out of...
	(build_comparison_op): Here.  Handle error return from build_new_op.

From-SVN: r279235