[Update] Add WATCHDOG_EXTERNAL_CHECKS

update.sh

@@ -160,6 +160,7 @@ CONFIG_ARRAY=(
   "USE_WATCHDOG"
   "WATCHDOG_NOTIFY_EMAIL"
   "WATCHDOG_NOTIFY_BAN"
+  "WATCHDOG_EXTERNAL_CHECKS"
   "SKIP_CLAMD"
   "SKIP_IP_CHECK"
   "ADDITIONAL_SAN"