build_kernel_image: Save kernel image

Save kernel image so it can be easily extracted as an artifact
from the build.

BUG=chrome-os-partner:41740
TEST='build_image --board=smaug' leaves vmlinuz.bin artifact

Change-Id: Ib040c2e0110b8fa75556c04353ce4a7fa4b0771f
Reviewed-on: https://chromium-review.googlesource.com/280892
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Commit-Queue: David Riley <davidriley@chromium.org>
diff --git a/build_kernel_image.sh b/build_kernel_image.sh
index 1af3a2a..ff43262 100755
--- a/build_kernel_image.sh
+++ b/build_kernel_image.sh
@@ -299,6 +299,12 @@
   error "Unknown arch: ${FLAGS_arch}"
 fi
 
+# Save the kernel as a .bin to allow it to be automatically extracted as
+# an artifact by cbuildbot.  Non .bin's need to be explicitly specified
+# and would require the entire set of artifacts to be specified.
+info "Saving kernel as ${FLAGS_working_dir}/vmlinuz.bin"
+cp ${kernel_image} ${FLAGS_working_dir}/vmlinuz.bin
+
 for image_type in $(get_image_types); do
   already_seen_rootfs=0
   for partition in $(get_partitions ${image_type}); do