+ifneq ($(O),)
ifeq ($(origin O), command line)
dummy := $(if $(shell test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
ABSOLUTE_O := $(shell cd $(O) ; pwd)
objtree := $(O)
endif
endif
+endif
-ifneq ($(OUTPUT),)
# check that the output directory actually exists
+ifneq ($(OUTPUT),)
OUTDIR := $(shell cd $(OUTPUT) && /bin/pwd)
$(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist))
endif