Copy artifact to kokoro_artifacts

Bug: 363237196
Test: kokoro
Change-Id: I7bcb517dc89ccba61b42f2d07e397695f8b7e93f
diff --git a/build/debian/kokoro/gcp_ubuntu_docker/build.sh b/build/debian/kokoro/gcp_ubuntu_docker/build.sh
index 2ea302b..4598d1c 100644
--- a/build/debian/kokoro/gcp_ubuntu_docker/build.sh
+++ b/build/debian/kokoro/gcp_ubuntu_docker/build.sh
@@ -6,3 +6,4 @@
 sudo losetup -D
 grep vmx /proc/cpuinfo || true
 sudo ./build.sh
+cp image.raw ${KOKORO_ARTIFACTS_DIR}