Use SO_REUSEPORT only on Linux, use SO_REUSEPORT_LB on FreeBSD
The SO_REUSEPORT socket option on Linux means something else on BSD based systems. On FreeBSD there's 1:1 option SO_REUSEPORT_LB, so we can use that.
Edited by Witold Krecicki
The SO_REUSEPORT socket option on Linux means something else on BSD based systems. On FreeBSD there's 1:1 option SO_REUSEPORT_LB, so we can use that.