Delete the kernel file when build config is changed

Now we have products of the same device type but with different kernel,
and we want to do incremental build on them.

Bug: 10133257
Change-Id: Iff4aae11e474d2822f02c62822bd028a5ba5b47a
diff --git a/core/cleanbuild.mk b/core/cleanbuild.mk
index 1d17f77..f32d0d1 100644
--- a/core/cleanbuild.mk
+++ b/core/cleanbuild.mk
@@ -182,6 +182,7 @@
 	$(PRODUCT_OUT)/*.txt \
 	$(PRODUCT_OUT)/*.xlb \
 	$(PRODUCT_OUT)/*.zip \
+	$(PRODUCT_OUT)/kernel \
 	$(PRODUCT_OUT)/data \
 	$(PRODUCT_OUT)/obj/APPS \
 	$(PRODUCT_OUT)/obj/NOTICE_FILES \