build: allow building an individual subdir without dependencies using NO_DEPS=1

QUILT=1 had the same effect, but it is sometimes useful to be able to do
this without quilt

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/subdir.mk

@@ -63,12 +63,12 @@ define subdir
     $(call warn,$(1),d,BD $(1)/$(bd))
     $(foreach target,$(SUBTARGETS) $($(1)/subtargets),
       $(foreach btype,$(buildtypes-$(bd)),
-        $(call warn_eval,$(1)/$(bd),t,T,$(1)/$(bd)/$(btype)/$(target): $(if $(QUILT),,$($(1)/$(bd)/$(btype)/$(target)) $(call $(1)//$(btype)/$(target),$(1)/$(bd)/$(btype))))
+        $(call warn_eval,$(1)/$(bd),t,T,$(1)/$(bd)/$(btype)/$(target): $(if $(NO_DEPS)$(QUILT),,$($(1)/$(bd)/$(btype)/$(target)) $(call $(1)//$(btype)/$(target),$(1)/$(bd)/$(btype))))
 		  $(call log_make,$(1)/$(bd),$(target),$(btype),$(filter-out __default,$(variant))) \
 			$(if $(findstring $(bd),$($(1)/builddirs-ignore-$(btype)-$(target))), || $(call ERROR,$(1),   ERROR: $(1)/$(bd) [$(btype)] failed to build.))
         $(if $(call diralias,$(bd)),$(call warn_eval,$(1)/$(bd),l,T,$(1)/$(call diralias,$(bd))/$(btype)/$(target): $(1)/$(bd)/$(btype)/$(target)))
       )
-      $(call warn_eval,$(1)/$(bd),t,T,$(1)/$(bd)/$(target): $(if $(QUILT),,$($(1)/$(bd)/$(target)) $(call $(1)//$(target),$(1)/$(bd))))
+      $(call warn_eval,$(1)/$(bd),t,T,$(1)/$(bd)/$(target): $(if $(NO_DEPS)$(QUILT),,$($(1)/$(bd)/$(target)) $(call $(1)//$(target),$(1)/$(bd))))
         $(foreach variant,$(if $(BUILD_VARIANT),$(BUILD_VARIANT),$(if $(strip $($(1)/$(bd)/variants)),$($(1)/$(bd)/variants),$(if $($(1)/$(bd)/default-variant),$($(1)/$(bd)/default-variant),__default))),
 			$(if $(BUILD_LOG),@mkdir -p $(BUILD_LOG_DIR)/$(1)/$(bd)/$(filter-out __default,$(variant)))
 			$(if $($(1)/autoremove),$(call rebuild_check,$(1)/$(bd),$(target),,$(filter-out __default,$(variant))))