Makefile: use GRUB_INSTALL_DIR in all places

Makefile

@@ -436,7 +436,7 @@ image_clean:
 	$(RM) "$(IMAGE_PART_FILE)"
 	$(RM) -r "$(GRUB_ASSEMBLE_DIR)"
 
-image_grub_lipinfo : $(IMAGE_DIR)/grub/lipinfo.cfg
+image_grub_lipinfo : $(IMAGE_DIR)$(GRUB_INSTALL_DIR)/lipinfo.cfg
 $(IMAGE_DIR)$(GRUB_INSTALL_DIR)/lipinfo.cfg : | $(WORKSPACE)
 	mkdir -p "$(IMAGE_DIR)$(GRUB_INSTALL_DIR)"
 	echo "#This file was generated by lipck." > "$@"