export $(call shvar,$(1))
endef
-define confvar
-$(foreach v,$(1),$(if $($(v)),y,n))
-endef
+empty:=
+space:= $(empty) $(empty)
+merge=$(subst $(space),,$(1))
+confvar=$(call merge,$(foreach v,$(1),$(if $($(v)),y,n)))
# file extension
ext=$(word $(words $(subst ., ,$(1))),$(subst ., ,$(1)))