Make avrdude program configurable

Makefile

@@ -2,11 +2,14 @@ OPTIMIZE = -O2
 CPPFLAGS += -DF_CPU=$(MCU_FREQ)
 override CFLAGS = -g --std=c99 -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET)
 override LDFLAGS =
+AVRDUDE_ARGS =
+
+# programs we are gonna use
 CC = avr-gcc
 OBJCOPY = avr-objcopy
 OBJDUMP = avr-objdump
 SIZE = avr-size
-AVRDUDE_ARGS =
+AVRDUDE = avrdude
 
 ifdef BOARD
 include boards/$(BOARD).mk
@@ -60,5 +63,5 @@ endif
 
 ifdef AVRDUDE_TYPE
 flash: $(PROG).hex
-	avrdude $(AVRDUDE_ARGS) -U flash:w:$(PROG).hex
+	$(AVRDUDE) $(AVRDUDE_ARGS) -U flash:w:$(PROG).hex
 endif