changed default hash mechanism to sha256

Makefile

@@ -515,8 +515,8 @@ $(IMAGE_FILE): $(IMAGE_PART_FILE) $(GRUB_ASSEMBLE_DIR)/mbr.img
 	@echo
 	@echo "Image is ready: $@"
 
-$(call ensure_unmount,image_deploy): $(IMAGE_FILE) $(IMAGE_FILE).sha1sum
-$(call ensure_unmount,image_deploy_vmdk): $(IMAGE_FILE:.img=.vmdk) $(IMAGE_FILE:.img=.vmdk).sha1sum
+$(call ensure_unmount,image_deploy): $(IMAGE_FILE) $(IMAGE_FILE).sha256sum
+$(call ensure_unmount,image_deploy_vmdk): $(IMAGE_FILE:.img=.vmdk) $(IMAGE_FILE:.img=.vmdk).sha256sum
 
 $(call ensure_unmount,image_clean):
 	$(RM) "$(IMAGE_PART_FILE)"
@@ -650,8 +650,8 @@ config_clean:
 %.vmdk : %.img
 	vboxmanage convertfromraw --format vmdk "$<" "$@"
 
-%.sha1sum : %
-	(cd "$$(dirname "$<")" && sha1sum "$$(basename "$<")") > "$@"
+%.sha256sum : %
+	(cd "$$(dirname "$<")" && sha256sum "$$(basename "$<")") > "$@"
 
 help:
 	@echo "Defaul Architecture: $(ARCH) ($(call altarch,$(ARCH)))"