OPTIMIZE_FOR_CPU:=$(ARCH)
-DL_DIR:=$(call qstrip,$(if $(CONFIG_DOWNLOAD_FOLDER), $(CONFIG_DOWNLOAD_FOLDER),$(TOPDIR)/dl))
+DL_DIR:=$(if $(call qstrip,$(CONFIG_DOWNLOAD_FOLDER)),$(call qstrip,$(CONFIG_DOWNLOAD_FOLDER)),$(TOPDIR)/dl)
BIN_DIR:=$(TOPDIR)/bin
INCLUDE_DIR:=$(TOPDIR)/include
SCRIPT_DIR:=$(TOPDIR)/scripts
export $(call shvar,$(1))
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)))