This patch was applied to gcc7 in aab8c7ba43 ("netbsd: add cross target"),
but it hasn't been brought forward to newer compilers that have the
same problem.
GCC 6 and (probably) GCC 4.9 also have the issue, but the patch
doesn't apply cleanly to them so I'm leaving them alone for now.
GCC 10, our current default, appears to have finally fixed this.
