image.mk: create default ubifs before calling legacy image build code

Signed-off-by: Felix Fietkau <[email protected]>

include/image.mk

@@ -485,7 +485,7 @@ define BuildImage
   $(foreach device,$(TARGET_DEVICES),$(call Device,$(device)))
   $(foreach device,$(LEGACY_DEVICES),$(call LegacyDevice,$(device)))
 
-  install-images: kernel_prepare $(foreach fs,$(filter-out ubifs,$(TARGET_FILESYSTEMS) $(fs-subtypes-y)),$(KDIR)/root.$(fs))
+  install-images: kernel_prepare $(foreach fs,$(filter-out $(if $(UBIFS_OPTS),,ubifs),$(TARGET_FILESYSTEMS) $(fs-subtypes-y)),$(KDIR)/root.$(fs))
 	$(foreach fs,$(TARGET_FILESYSTEMS),
 		$(call Image/Build,$(fs))
 	)