AP_Scripting: allow AP_SCRIPTING_ENABLED to come from hwdef files

libraries/AP_Scripting/AP_Scripting.cpp

@@ -13,6 +13,10 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "AP_Scripting_config.h"
+
+#if AP_SCRIPTING_ENABLED
+
 #include <AP_Scripting/AP_Scripting.h>
 #include <AP_HAL/AP_HAL.h>
 #include <GCS_MAVLink/GCS.h>
@@ -364,3 +368,5 @@ namespace AP {
         return AP_Scripting::get_singleton();
     }
 }
+
+#endif  // AP_SCRIPTING_ENABLED