Fix go2rtc getting env var (#7052)

docker/rootfs/etc/s6-overlay/s6-rc.d/go2rtc/run

@@ -43,6 +43,8 @@ function get_ip_and_port_from_supervisor() {
     export FRIGATE_GO2RTC_WEBRTC_CANDIDATE_INTERNAL="${ip_address}:${webrtc_port}"
 }
 
+export LIBAVFORMAT_VERSION_MAJOR=$(ffmpeg -version | grep -Po 'libavformat\W+\K\d+')
+
 if [[ ! -f "/dev/shm/go2rtc.yaml" ]]; then
     echo "[INFO] Preparing go2rtc config..."