test for LED_BUILTIN existence

Author: d-a-v

variants/generic/common.h

@@ -71,9 +71,11 @@ static const uint8_t A0 = PIN_A0;
 #define SERIAL_PORT_HARDWARE       Serial
 #define SERIAL_PORT_HARDWARE_OPEN  Serial1
 
+#ifdef LED_BUILTIN
 #ifdef __cplusplus
 extern "C"
 #endif
 const int BUILTIN_LED __attribute__((deprecated, weak)) = LED_BUILTIN;
+#endif
 
 #endif /* GENERIC_COMMON_H */