static: temporarily skip containerd package if it's not built

Moby's cross target currently doesn't include containerd binaries,
so skipping containerd to prevent publishing an empty tar.

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

static/build-static

@@ -249,7 +249,10 @@ case ${TARGETOS} in
 		(
 			set -x
 			tar -C "${buildDir}" -c -z -f "${buildDir}/docker-engine-${ENGINE_VERSION}.tgz" docker-engine
-			tar -C "${buildDir}" -c -z -f "${buildDir}/containerd-${CONTAINERD_PKG_VER#v}.tgz" containerd
+			if [ "$(ls -A "${containerdBuildDir}")" ]; then
+				# FIXME(thaJeztah) moby cross-compile currently doesn't include containerd binaries
+				tar -C "${buildDir}" -c -z -f "${buildDir}/containerd-${CONTAINERD_PKG_VER#v}.tgz" containerd
+			fi
 		)
 		;;
 	windows)