Dockerfile: build image with alpine

scripts/build-docker

@@ -8,12 +8,6 @@ IMAGEDIR=${BUILDDIR}/image-docker
 mkdir -p ${IMAGEDIR}
 cp ${BINARYDIR}/etcd ${BINARYDIR}/etcdctl ${IMAGEDIR}
 
-cat <<DF > ${IMAGEDIR}/Dockerfile
-FROM scratch
-ADD etcd /
-ADD etcdctl /
-EXPOSE 2379 2380
-ENTRYPOINT ["/etcd"]
-DF
+cat ./Dockerfile > ${IMAGEDIR}/Dockerfile
 
 docker build -t quay.io/coreos/etcd:${1} ${IMAGEDIR}