The --no-run-if-empty option is a GNU extension and the long version isn't supported by *BSD variants.
Instead use the short version (-r) which is present, but ignored as it is the default behavior, in at least FreeBSD: https://www.freebsd.org/cgi/man.cgi?xargs
MaraDNS is a lightweight self-hosting DNS server. This patch adds
support for adding records to zone files stored on the server in the
format expected by MaraDNS. Path to the file should be exported in
MARA_ZONE_FILE environment variable. To reload the configuration
automatically, the user must provide path to the pid file of duende (the
daemonization tool that ships with MaraDNS) in MARA_DUENDE_PID_PATH
(--pid argument to duende).