The sysctl interface on FreeBSD is ever so slightly different from OpenBSD. Especially, we have a different number of elements in the mib name, so namelen becomes a variable initialised inside the #ifdef'ed code, and the calculation of the number of processes in the result differs between OpenBSD and FreeBSD. Lastly, we need to process the results differently on FreeBSD. Differential Revision: https://phabricator.services.mozilla.com/D235080