Add NetBSD to CI #3890
Description
x86_64-unknown-netbsd is a tier two target, and it looks like cirrus CI might now have support for it cirruslabs/cirrus-ci-docs#970. We should try to get it in our CI.
Cc @semarie if you are interested in working on this since I know you review the OpenBSD support. I don't think we could add OpenBSD since it is tier 3, but NetBSD would at least get something in the same family tested.