Add ARM basic bootloader build

arm/makefile

@@ -0,0 +1,25 @@
+CC = arm-none-eabi-gcc
+LD = arm-none-eabi-gcc
+CXX = arm-none-eabi-g++
+OBJCOPY = arm-none-eabi-objcopy
+
+linker_script = bootloader.ld
+
+CFLAGS = -march=armv6-m -g -ffunction-sections -fdata-sections -O2
+CXXFLAGS = $(CFLAGS) -std=c++20 -fno-exceptions
+LDFLAGS = -march=armv6-m -g --specs=nano.specs --specs=nosys.specs -Wl,--gc-sections -Wl,-T$(linker_script) -O2
+
+all: bootloader.bin
+
+%.bin: %.elf
+	$(OBJCOPY) -O binary $< $@
+
+bootloader.elf: main.o vector_table.o
+
+%.elf:
+	$(LD) $(LDFLAGS) -o $@ $^
+
+.PHONY: clean
+
+clean:
+	rm -rf *.elf *.bin *.o