Simplify build system mandatory parameter/variable sanity checks.

LUFA/Build/lufa.avrdude.in

@@ -44,12 +44,8 @@ AVRDUDE_PORT        ?= usb
 AVRDUDE_FLAGS      ?= -U flash:w:$(TARGET).hex
 
 # Sanity check the user MCU and TARGET makefile options
-ifeq ($(MCU),)
-   $(error Makefile MCU value not set.)
-endif
-ifeq ($(TARGET),)
-   $(error Makefile TARGET value not set.)
-endif
+MCU                ?= $(error Makefile MCU value not set.)
+TARGET             ?= $(error Makefile TARGET value not set.)
 
 program: $(TARGET).hex
 	@echo $(MSG_AVRDUDE_CMD) Programming device \"$(MCU)\" with settings \"$(AVRDUDE_FLAGS)\" using \"$(AVRDUDE_PROGRAMMER)\" on port \"$(AVRDUDE_PORT)\"

LUFA/Build/lufa.build.in

@@ -64,24 +64,12 @@ MSG_OBJCPY_CMD  = '  [OBJCPY]  :'
 MSG_OBJDMP_CMD  = ' [OBJDMP]  :'
 
 # Sanity check the user MCU, TARGET, ARCH, SRC, F_USB and LUFA_PATH makefile options
-ifeq ($(TARGET),)
-   $(error Makefile TARGET value not set.)
-endif
-ifeq ($(ARCH),)
-   $(error Makefile ARCH value not set.)
-endif
-ifeq ($(MCU),)
-   $(error Makefile MCU value not set.)
-endif
-ifeq ($(SRC),)
-   $(error Makefile SRC value not set.)
-endif
-ifeq ($(F_USB),)
-   $(error Makefile F_USB value not set.)
-endif
-ifeq ($(LUFA_PATH),)
-   $(error Makefile LUFA_PATH value not set.)
-endif
+MCU            ?= $(error Makefile MCU value not set.)
+TARGET         ?= $(error Makefile TARGET value not set.)
+ARCH           ?= $(error Makefile ARCH value not set.)
+SRC            ?= $(error Makefile SRC value not set.)
+F_USB          ?= $(error Makefile F_USB value not set.)
+LUFA_PATH      ?= $(error Makefile LUFA_PATH value not set.)
 
 # Default values of user-supplied variables
 BOARD          ?= NONE

LUFA/Build/lufa.dfu.in

@@ -37,15 +37,13 @@ LUFA_BUILD_OPTIONAL_VARS  +=
 # -----------------------------------------------------------------------------
 
 # Output Messages
+MSG_COPY_CMD    = ' [CP]      :'
+MSG_REMOVE_CMD  = ' [RM]      :'
 MSG_DFU_CMD     = ' [DFU]     :'
 
 # Sanity check the user MCU and TARGET makefile options
-ifeq ($(MCU),)
-   $(error Makefile MCU value not set.)
-endif
-ifeq ($(TARGET),)
-   $(error Makefile TARGET value not set.)
-endif
+MCU            ?= $(error Makefile MCU value not set.)
+TARGET         ?= $(error Makefile TARGET value not set.)
 
 flip: $(TARGET).hex
 	@echo $(MSG_DFU_CMD) Programming FLASH with batchisp using \"$(TARGET).hex\"
@@ -54,11 +52,13 @@ flip: $(TARGET).hex
 	batchisp -hardware usb -device $(MCU) -operation start reset 0
 
 flip-ee: $(TARGET).eep
+	@echo $(MSG_DFU_CMD) Copying EEP file to temporary file \"$(TARGET)eep.hex\"
 	cp $(TARGET).eep $(TARGET)eep.hex
 	@echo $(MSG_DFU_CMD) Programming EEPROM with batchisp using \"$(TARGET).eep\"
 	batchisp -hardware usb -device $(MCU) -operation memory EEPROM erase
 	batchisp -hardware usb -device $(MCU) -operation memory EEPROM loadbuffer $(TARGET)eep.hex program
 	batchisp -hardware usb -device $(MCU) -operation start reset 0
+	@echo $(MSG_DFU_CMD) Removing temporary file \"$(TARGET)eep.hex\"
 	rm $(TARGET)eep.hex
 	
 dfu: $(TARGET).hex

LUFA/Build/lufa.sources.in

@@ -36,12 +36,8 @@ LUFA_BUILD_OPTIONAL_VARS  +=
 # -----------------------------------------------------------------------------
 
 # Sanity check the user LUFA_PATH and ARCH makefile options
-ifeq ($(LUFA_PATH),)
-   $(error Makefile LUFA_PATH value not set.)
-endif
-ifeq ($(ARCH),)
-   $(error Makefile ARCH value not set.)
-endif
+ARCH           ?= $(error Makefile ARCH value not set.)
+LUFA_PATH      ?= $(error Makefile LUFA_PATH value not set.)
 
 # Allow LUFA_ROOT_PATH to be overridden elsewhere to support legacy LUFA makefiles
 LUFA_ROOT_PATH ?= $(LUFA_PATH)