Makefile snippet: json -> shell env var

Makefile-json-to-var

# delete a line in an environment file that sets a var
# env_del(var,file)
define env_del
	@{ [[ ! -e "$(2)" ]] || sed -i /'$(1)='/d $(2); } || :
endef

# given a env var name and json file, minify and add to specified file
# env_minify_json(var, json, dest)
define env_minify_json
  $(call env_del,$(1),$(3))
  @echo "$(1)=$$(jq -c . < $(2))" >> $(3)
endef