image.mk: export the FILESYSTEM variable to build commands

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

SVN-Revision: 45251

include/image.mk

@@ -353,7 +353,7 @@ define Device/ExportVar
   $(1) : $(2):=$$($(2))
 
 endef
-Device/Export = $(foreach var,$(DEVICE_VARS) KERNEL KERNEL_INITRAMFS,$(call Device/ExportVar,$(1),$(var)))
+Device/Export = $(foreach var,$(DEVICE_VARS) KERNEL KERNEL_INITRAMFS FILESYSTEM,$(call Device/ExportVar,$(1),$(var)))
 
 define Device/Check
   _TARGET = $$(if $$(filter $(PROFILE),$$(PROFILES)),install,install-disabled)