Add rule for building the lk bootloader.

Change-Id: Ia87fe202ee0a69f008a355a8bac63df667d17868
diff --git a/packages.mk b/packages.mk
index 2aa3a49..f44599f 100644
--- a/packages.mk
+++ b/packages.mk
@@ -13,3 +13,4 @@
 # limitations under the License.
 
 $(eval $(call make-pbuilder-bsp-package-target,u-boot-mkimage,bootloader/mtk-tools/u-boot-mkimage))
+$(eval $(call make-pbuilder-bsp-package-target,lk-bootloader,bootloader))