[add] clean command

Author: whj4674672

projects/uf2_boot/makefile.targets

@@ -1,3 +1,6 @@
-
+clean2:
+	-$(RM) $(CC_DEPS)$(C++_DEPS)$(C_UPPER_DEPS)$(CXX_DEPS)$(SECONDARY_FLASH)$(SECONDARY_SIZE)$(ASM_DEPS)$(S_UPPER_DEPS)$(C_DEPS)$(CPP_DEPS)
+	-$(RM) $(OBJS) *.elf
+	-@echo ' '
 
 *.elf: $(wildcard E:/project/art-pi-sdk-github/sdk-bsp-stm32h750-realthread-artpi/projects/uf2_boot/GCC/link.lds)