Do not fetch tools when running on qemu.

os/Makefile

@@ -71,10 +71,9 @@ disasm-vim: kernel
 	@vim $(DISASM_TMP)
 	@rm $(DISASM_TMP)
 
-run: tools run-inner
+run: run-inner
 
-tools:
-	(which $(K210-BURNER)) || (cd .. && git clone https://github.com/sipeed/kflash.py.git && mv kflash.py tools)
+	
 
 run-inner: build
 ifeq ($(BOARD),qemu)
@@ -86,6 +85,7 @@ ifeq ($(BOARD),qemu)
 		-drive file=$(FS_IMG),if=none,format=raw,id=x0 \
         -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0
 else
+	(which $(K210-BURNER)) || (cd .. && git clone https://github.com/sipeed/kflash.py.git && mv kflash.py tools)
 	@cp $(BOOTLOADER) $(BOOTLOADER).copy
 	@dd if=$(KERNEL_BIN) of=$(BOOTLOADER).copy bs=$(K210_BOOTLOADER_SIZE) seek=1
 	@mv $(BOOTLOADER).copy $(KERNEL_BIN)
@@ -100,4 +100,4 @@ debug: build
 		tmux split-window -h "riscv64-unknown-elf-gdb -ex 'file $(KERNEL_ELF)' -ex 'set arch riscv:rv64' -ex 'target remote localhost:1234'" && \
 		tmux -2 attach-session -d
 
-.PHONY: build env kernel clean disasm disasm-vim run-inner tools
+.PHONY: build env kernel clean disasm disasm-vim run-inner