cmd/coordinator: skip netbsd-386 builds for now
cmd/coordinator: skip netbsd-386 builds for now

Updates golang/go#19339

Change-Id: Id9e5247c0ffbddf4bcf0d807840399d3a5dd83c5
Reviewed-on: https://go-review.googlesource.com/37622
Reviewed-by: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>

golang/build,golang/build,golang/build,golang/build