build: add locking around dtc call after running mkits.sh

mkits.sh creates a root.*.pagesync file with padding, which is global, and
the generated .its files reference it. Since dtc reads this file, it must
not run at the same time as mkits.sh
Fixes generating itb images with broken rootfs.

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

include/image-commands.mk

@@ -391,8 +391,8 @@ define Build/fit
 		$(if $(DEVICE_DTS_OVERLAY),$(foreach dtso,$(DEVICE_DTS_OVERLAY), -O $(dtso):$(KERNEL_BUILD_DIR)/image-$(dtso).dtbo)) \
 		-c $(if $(DEVICE_DTS_CONFIG),$(DEVICE_DTS_CONFIG),"config-1") \
 		-A $(LINUX_KARCH) -v $(LINUX_VERSION), gen-cpio$(if $(TARGET_PER_DEVICE_ROOTFS),.$(ROOTFS_ID/$(DEVICE_NAME))))
-	PATH=$(LINUX_DIR)/scripts/dtc:$(PATH) mkimage $(if $(findstring external,$(word 3,$(1))),\
-		-E -B 0x1000 $(if $(findstring static,$(word 3,$(1))),-p 0x1000)) -f $@.its $@.new
+	$(call locked,PATH=$(LINUX_DIR)/scripts/dtc:$(PATH) mkimage $(if $(findstring external,$(word 3,$(1))),\
+		-E -B 0x1000 $(if $(findstring static,$(word 3,$(1))),-p 0x1000)) -f $@.its $@.new)
 	@mv $@.new $@
 endef