As far as I can tell, this check has been
non-functional since it was introduced.

This cuts 57k off cmd/go and 70k off cmd/compile.

Based on golang.org/cl/24710 by Josh Bleecher Snyder.

Change-Id: I1162a066971df1a067b50afa1cfa0819a6913574
Reviewed-on: https://go-review.googlesource.com/27830Reviewed-by: David Crawshaw <crawshaw@golang.org>