Properly always copy firmware

This finishes fixing #2314, which mostly copies the firmware when compiling.
However, it misses `:teensy`, `:avrdude` and most importantly, `:production`

tmk_core/avr.mk

@@ -124,7 +124,7 @@ qmk: $(BUILD_DIR)/$(TARGET).hex
 program: $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).eep check-size
 	$(PROGRAM_CMD)
 
-teensy: $(BUILD_DIR)/$(TARGET).hex check-size
+teensy: $(BUILD_DIR)/$(TARGET).hex check-size cpfirmware
 	$(TEENSY_LOADER_CLI) -mmcu=$(MCU) -w -v $(BUILD_DIR)/$(TARGET).hex
 
 BATCHISP ?= batchisp
@@ -169,7 +169,7 @@ dfu-ee: $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).eep
 	fi
 	$(DFU_PROGRAMMER) $(MCU) reset
 
-avrdude: $(BUILD_DIR)/$(TARGET).hex check-size
+avrdude: $(BUILD_DIR)/$(TARGET).hex check-size cpfirmware
 	if $(GREP) -q -s Microsoft /proc/version; then \
 		echo 'ERROR: AVR flashing cannot be automated within the Windows Subsystem for Linux (WSL) currently. Instead, take the .hex file generated and flash it using AVRDUDE, AVRDUDESS, or XLoader.'; \
 	else \
@@ -264,7 +264,7 @@ bootloader:
 	echo -e "BootloaderDFU.hex copied to $(TARGET)_bootloader.hex"
 	cp lib/lufa/Bootloaders/DFU/BootloaderDFU.hex $(TARGET)_bootloader.hex
 
-production: $(BUILD_DIR)/$(TARGET).hex bootloader
+production: $(BUILD_DIR)/$(TARGET).hex bootloader cpfirmware
 	@cat $(BUILD_DIR)/$(TARGET).hex | awk '/^:00000001FF/ == 0' > $(TARGET)_production.hex
 	@cat $(TARGET)_bootloader.hex >> $(TARGET)_production.hex
 	echo "File sizes:"