Fixed compilation error

Author: timkoers

libraries/ESP32/examples/Serial/Interrupt/Interrupt.ino

@@ -8,7 +8,7 @@ static volatile size_t inputBufferLength = 0;
 static void IRAM_ATTR onSerialRX(uint8_t character, void* user_arg){
 
 	// Cast the user_arg back to a array
-	char buffer[] = (char*)user_arg;
+	char buffer* = (char*)user_arg;
 
 	if(inputBufferLength < BUFFER_SIZE){
 		buffer[inputBufferLength++] = (char)character;