Prior to this commit CGO was used in OpenBSD implementation of
Process.CmdlineSliceWithContext() for parsing the "kern.proc.args"
sysctl output. It requires some pointer arithmetics and raw pointer
dereferencing.
Having CGO in the "process" module prevents it from being go vet'ted
on any platform other than OpenBSD. In order to overcome this
limitation, the sysctl output parsing was reimplemented without raw
pointer deferencing. The resulting code might be slightly slower
than the original one, but it is cleaner and safer.
Since this fix allows go vet with GOOS=openbsd to run without any
issues on all platforms, openbsd entries were also added to the "vet"
Makefile target.
Co-authored-by: Sergey Vinogradov <cbrpnk@gmail.com>