Arduino.mk: allow user avrdude flags

libraries/AP_Common/Arduino.mk

@@ -364,6 +364,9 @@ F_CPU			:=	$(shell grep $(BOARD).build.f_cpu $(BOARDFILE) | cut -d = -f 2)
 HARDWARE_CORE		:=	$(shell grep $(BOARD).build.core $(BOARDFILE) | cut -d = -f 2)
 UPLOAD_SPEED		:=	$(shell grep $(BOARD).upload.speed $(BOARDFILE) | cut -d = -f 2)
 
+# User can define USERAVRDUDEFLAGS = -V in their config.mk to skip verification
+USERAVRDUDEFLAGS ?= 
+
 ifeq ($(UPLOAD_PROTOCOL),)
   UPLOAD_PROTOCOL	:=	$(shell grep $(BOARD).upload.protocol $(BOARDFILE) | cut -d = -f 2)
 endif
@@ -431,7 +434,7 @@ all:	$(SKETCHELF) $(SKETCHEEP) $(SKETCHHEX)
 
 .PHONY: upload
 upload: $(SKETCHHEX)
-	$(AVRDUDE) -c $(UPLOAD_PROTOCOL) -p $(MCU) -P $(PORT) -b$(UPLOAD_SPEED) -U flash:w:$(SKETCHHEX):i
+	$(AVRDUDE) -c $(UPLOAD_PROTOCOL) -p $(MCU) -P $(PORT) -b$(UPLOAD_SPEED) $(USERAVRDUDEFLAGS) -U flash:w:$(SKETCHHEX):i
 
 configure:
 	$(warning WARNING - A $(SKETCHBOOK)/config.mk file has been written)