Fix weaked serialEventRun() not being called

Fixes #985

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

Author: fpistm

cores/arduino/WSerial.cpp

@@ -1,6 +1,6 @@
 #include "WSerial.h"
 
-void serialEventRun(void)
+WEAK void serialEventRun(void)
 {
 #if defined(HAVE_HWSERIAL1)
   if (serialEvent1 && Serial1.available()) {

cores/arduino/WSerial.h

@@ -165,6 +165,6 @@ extern void serialEvent10(void) __attribute__((weak));
 extern void serialEventLP1(void) __attribute__((weak));
 #endif /* HAL_UART_MODULE_ENABLED  && !HAL_UART_MODULE_ONLY */
 
-extern void serialEventRun(void) __attribute__((weak));
+extern void serialEventRun(void);
 
 #endif /* WIRING_SERIAL_H */

cores/arduino/main.cpp

@@ -62,9 +62,7 @@ int main(void)
     CoreCallback();
 #endif
     loop();
-    if (serialEventRun) {
-      serialEventRun();
-    }
+    serialEventRun();
   }
 
   return 0;