SITL: Change build errors

libraries/SITL/SIM_Buzzer.h

@@ -40,6 +40,13 @@ public:
 
     AP_Int8  _enable;  // enable buzzer sim
     AP_Int8  _pin;
+#ifdef WITH_SITL_TONEALARM
+    bool was_on;
+
+    uint32_t on_time;
+
+    bool prep_done;
+#endif
 };
 
 }