# ----- define these variables
# CACHED_FILES     = $(TOPDIR)/VERSION
# CACHED_VARS      = VERSION
.PHONY: cache

CACHE_FILE_MK ?= .cache.mk

# if not checked against MAKECMDGOALS, a standard rule kicks in from rules.mk,
# and $(CACHE_FILE_MK) is remade with the clean target
all: cache
ifneq ($(foreach g,all cache,$(findstring $(g),$(MAKECMDGOALS))),)
cache: $(CACHE_FILE_MK)
$(CACHE_FILE_MK): $(CACHED_FILES) $(JWBDIR)/make/cache.mk
ifeq ($(wildcard $(CACHE_FILE_MK)),)
	@echo $(foreach v,$(CACHED_VARS),$v := $(value $(v))EOL) | $(SED) 's/EOL */\n/g;' | $(GREP) . | tee $@.tmp
	mv $@.tmp $@
else
	rm $@
	make $@
endif
endif
clean: clean-cache
clean-cache:
	$(RM) -f $(CACHE_FILE_MK)