AP_GPS: allow compilation with HAL_LOGGING_ENABLED false

libraries/AP_GPS/AP_GPS.cpp

@@ -2254,6 +2254,7 @@ bool AP_GPS::get_undulation(uint8_t instance, float &undulation) const
     return true;
 }
 
+#if HAL_LOGGING_ENABLED
 // Logging support:
 // Write an GPS packet
 void AP_GPS::Write_GPS(uint8_t i)
@@ -2310,6 +2311,7 @@ void AP_GPS::Write_GPS(uint8_t i)
     };
     AP::logger().WriteBlock(&pkt2, sizeof(pkt2));
 }
+#endif
 
 /*
   get GPS based yaw

libraries/AP_GPS/AP_GPS_DroneCAN.cpp

@@ -526,10 +526,12 @@ void AP_GPS_DroneCAN::handle_status_msg(const ardupilot_gnss_Status& msg)
     healthy = msg.healthy;
     status_flags = msg.status;
     if (error_code != msg.error_codes) {
+#if HAL_LOGGING_ENABLED
         AP::logger().Write_MessageF("GPS %d: error changed (0x%08x/0x%08x)",
                                     (unsigned int)(state.instance + 1),
                                     error_code,
                                     msg.error_codes);
+#endif
         error_code = msg.error_codes;
     }
 }

libraries/AP_GPS/GPS_Backend.cpp

@@ -23,6 +23,7 @@
 #include <time.h>
 #include <AP_Common/time.h>
 #include <AP_InternalError/AP_InternalError.h>
+#include <AP_AHRS/AP_AHRS.h>
 
 #define GPS_BACKEND_DEBUGGING 0