dns/dnsmasq: Fix --dhcp-relay not working on FreeBSD

PR: 283138
MFH: 2024Q2
Reported by: Harald Schmalzbauer
Obtained from: Simon Kelley, https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=5a1f2c577db58ea47727f1b6900c0be25e6db205

(cherry picked from commit b572f527d6423f318197a98802cb58b8e20929d7)