release: fix ports checkout if /usr/ports does not exist

Reported by:	Yasuhiro Kimura
Sponsored by:	Rubicon Communications, LLC ("Netgate")

(cherry picked from commit c0dbc49ab3)

release/release.sh

@@ -213,6 +213,8 @@ chroot_setup() {
 	if [ -z "${NOPORTS}" ] && [ -z "${PORTS_UPDATE_SKIP}" ]; then
 		if [ -d "${CHROOTDIR}/usr/ports/.git" ]; then
 			git -C ${CHROOTDIR}/usr/ports pull -q
+		else
+			${VCSCMD} ${PORT} -b ${PORTBRANCH} ${CHROOTDIR}/usr/ports
 		fi
 	fi