sys/capability.h will be removed before FreeBSD 13. The (now) correct header to use on all supported (and some unsupported) versions of FreeBSD is sys/capsicum.h. There's no need for autoconf checks etc. to check for both (in the ports tree) but upstream may want to if there's a desire to build on older releases.
I'll open a bug in upstream and then add a patch on ports
A commit references this bug: Author: garga Date: Tue Nov 6 17:17:33 UTC 2018 New revision: 484310 URL: https://svnweb.freebsd.org/changeset/ports/484310 Log: - Do not include deprecated header sys/capability.h [1] - Remove unnecessary include of bsd.port.pre.mk - Add LICENSE_FILE - Fix USES order - Bump PORTREVISION PR: 233008 [1] Reported by: emaste@ [1] Sponsored by: Rubicon Communications, LLC (Netgate) Changes: head/net/tcpdump/Makefile
PR submitted to upstream at https://github.com/the-tcpdump-group/tcpdump/pull/715