packaging: Add infra to push the td-shim builder image

Let's add the needed infra for only building and pushing the td-shim
builder image to the Kata Containers' quay.io registry.

Fixes: #5479

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

tools/packaging/static-build/td-shim/build.sh

@@ -32,10 +32,13 @@ package_output_dir="${package_output_dir:-}"
 
 container_image="${CC_BUILDER_REGISTRY}:td-shim-${tdshim_toolchain}-$(get_last_modification ${repo_root_dir} ${script_dir})"
 
-sudo docker pull ${container_image} || sudo docker build \
-	--build-arg RUST_TOOLCHAIN="${tdshim_toolchain}" \
-	-t "${container_image}" \
-	"${script_dir}"
+sudo docker pull ${container_image} || \
+	(sudo docker build \
+		--build-arg RUST_TOOLCHAIN="${tdshim_toolchain}" \
+		-t "${container_image}" \
+		"${script_dir}" && \
+	 # No-op unless PUSH_TO_REGISTRY is exported as "yes"
+	 push_to_registry "${container_image}")
 
 sudo docker run --rm -i -v "${repo_root_dir}:${repo_root_dir}" \
 	-w "${PWD}" \