[SYS] Fix for build error with MDNS_SD (#2239)

* Fix for build error with MDNS_SD

* Update environments.ini

environments.ini

@@ -257,6 +257,7 @@ build_flags =
   '-DMQTT_USER=""'
   '-DMQTT_PASS=""'
   '-DMQTT_PORT="1883"'
+  '-DMDNS_SD=true'
   '-DDEEP_SLEEP_IN_US=120000000' ; Deep sleep for a period of time to conserve battery
   '-DESP32_EXT0_WAKE_PIN=GPIO_NUM_14' ;Should a water leak be detected immediatly wake the ESP32 and report the problem
   '-DESP32_EXT0_WAKE_PIN_STATE=0' ;Should a water leak be detected immediatly wake the ESP32 and report the problem, sensor state to look for wakeup