CL 45052 added them to mkerrors.sh but they weren't generated on NetBSD. Do so now.

Change-Id: I314b0b7b203aba910a5733f9fbb63b1a0e6ccecf
Reviewed-on: https://go-review.googlesource.com/137595
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>