在makefile中打印输出信息的方法是：$(warning xxxxx)或者$(error xxxxx)
输出变量方式为：$(warning $(XXX))
root@bogon runtime]# grep CLHCMD -rn *
arch/amd64-options.mk:28:CLHCMD := cloud-hypervisor
arch/arm64-options.mk:21:CLHCMD := cloud-hypervisor
Makefile:141:CLHPATH := $(CLHBINDIR)/$(CLHCMD)
Makefile:142:CLHVALIDHYPERVISORPATHS := [\"$(CLHBINDIR)/$(CLHCMD)\"]
Makefile:264:$(warning $(CLHCMD))
Makefile:265:ifneq (,$(CLHCMD))
Makefile.2.0:142:CLHPATH := $(CLHBINDIR)/$(CLHCMD)
Makefile.2.0:143:CLHVALIDHYPERVISORPATHS := [\"$(CLHBINDIR)/$(CLHCMD)\"]
Makefile.2.0:266:ifneq (,$(CLHCMD))
[root@bogon runtime]# grep options.mk -rn *
Makefile:35:ARCH_FILE_SUFFIX = -options.mk
Makefile.2.0:35:ARCH_FILE_SUFFIX = -options.mk
[root@bogon runtime]#
