[STM32] Define VERSION_BLINK_PIN only if LED_BUILTIN is defined

Not all STM32 boards have a LED_BUILTIN.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

Boards.h

@@ -854,7 +854,9 @@ writePort(port, value, bitmask):  Write an 8 bit port.
 #define TOTAL_ANALOG_PINS       NUM_ANALOG_INPUTS
 #define TOTAL_PINS              NUM_DIGITAL_PINS
 #define TOTAL_PORTS             MAX_NB_PORT
+#ifdef LED_BUILTIN
 #define VERSION_BLINK_PIN       LED_BUILTIN
+#endif
 // PIN_SERIALY_RX/TX defined in the variant.h
 #define IS_PIN_DIGITAL(p)       (digitalPinIsValid(p) && !pinIsSerial(p))
 #define IS_PIN_ANALOG(p)        ((p >= A0) && (p < (A0 + TOTAL_ANALOG_PINS)) && !pinIsSerial(p))