printenv:
$(foreach V,$(sort $(.VARIABLES)),\
$(if $(filter-out default automatic,\
$(origin $V)),$(warning $V=$($V) ($(value $V)))))
or - new variables only:
VARS_OLD := $(.VARIABLES)
CUR-DIR := $(shell pwd)
LOG-DIR := $(CUR-DIR)/make-logs
$(foreach v, \
$(filter-out $(VARS_OLD) VARS_OLD,$(.VARIABLES)), \
$(info $(v) = $($(v))))