define assigned_varname
$(if $(findstring =,$(1)),$(firstword $(subst =, ,$(1))) )
endef
-ASSIGNED=$(foreach flag,$(MAKEFLAGS),$(call assigned_varname,$(flag)))
+ASSIGNED=$(filter-out stage1 stage1iter,$(foreach flag,$(MAKEFLAGS),$(call assigned_varname,$(flag))))
SAVED_VARS=$(sort $(STATIC_VARS) $(ASSIGNED))
envfrompreviousrun.mk:
@echo "# do not edit" > $@