## sets the value to literal empty string
SOMEVARIABLE := aaa

.PHONY: default
default:
	@echo "showing the value of SOMEVARIABLE inside this make rule:"
	@env | grep SOMEVARIABLE || echo "(not set)"
	@echo "showing the value of ANOTHERVARIABLE inside this make rule:"
	@env | grep ANOTHERVARIABLE || echo "(not set)"