Add multiple configuration options for a minimized build (GPS,WiFi,BT,MQTT,Screen). (#3469)

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/mesh/MeshService.h

@@ -23,9 +23,10 @@ extern Allocator<meshtastic_MqttClientProxyMessage> &mqttClientProxyMessagePool;
  */
 class MeshService
 {
+#if HAS_GPS
     CallbackObserver<MeshService, const meshtastic::GPSStatus *> gpsObserver =
         CallbackObserver<MeshService, const meshtastic::GPSStatus *>(this, &MeshService::onGPSChanged);
-
+#endif
     /// received packets waiting for the phone to process them
     /// FIXME, change to a DropOldestQueue and keep a count of the number of dropped packets to ensure
     /// we never hang because android hasn't been there in a while
@@ -132,10 +133,11 @@ class MeshService
     ErrorCode sendQueueStatusToPhone(const meshtastic_QueueStatus &qs, ErrorCode res, uint32_t mesh_packet_id);
 
   private:
+#if HAS_GPS
     /// Called when our gps position has changed - updates nodedb and sends Location message out into the mesh
     /// returns 0 to allow further processing
     int onGPSChanged(const meshtastic::GPSStatus *arg);
-
+#endif
     /// Handle a packet that just arrived from the radio.  This method does _ReliableRouternot_ free the provided packet.  If it
     /// needs to keep the packet around it makes a copy
     int handleFromRadio(const meshtastic_MeshPacket *p);