NetBSD 8.0(beta) ships with KERN_PROC_PATHNAME in sysctl(2).
Older NetBSD versions can use argv[0] parsing fallback.

This code section is partly shared with FreeBSD.

Signed-off-by: Kamil Rytarowski <n54@gmx.com>
Message-id: 20171028194833.23858-1-n54@gmx.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>