Build etcd image and push it to gcr.io

cluster/images/etcd/Dockerfile

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+FROM scratch
+MAINTAINER  Dawn Chen <dawnchen@google.com>
+
+ADD ./etcd /usr/local/bin/etcd
+ADD ./etcdctl /usr/local/bin/etcdctl

cluster/images/etcd/Makefile

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+.PHONY:	clean build push
+
+IMAGE = etcd
+TAG = 2.0.8
+OUTPUT_DIR = $(IMAGE)-v$(TAG)-linux-amd64
+
+clean:
+	rm -rf $(OUTPUT_DIR) $(IMAGE)-v$(TAG)-linux-amd64.tar.gz etcd etcdctl
+
+build: clean
+	curl -L -O https://github.com/coreos/etcd/releases/download/v$(TAG)/$(IMAGE)-v$(TAG)-linux-amd64.tar.gz
+	tar xzvf $(IMAGE)-v$(TAG)-linux-amd64.tar.gz
+	cp $(OUTPUT_DIR)/etcd .
+	cp $(OUTPUT_DIR)/etcdctl .
+	docker build -t gcr.io/google_containers/$(IMAGE):$(TAG) .
+
+push:	build
+	gcloud preview docker push gcr.io/google_containers/$(IMAGE):$(TAG)
+
+all:	push