tools: Move toybox to ./tools and use a multi-stage build

Also use c-compile to compile it

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

tools/toybox-media/Dockerfile

@@ -0,0 +1,18 @@
+FROM linuxkit/c-compile:f52f485825c890d581e82a62af6906c1d33d8e5d@sha256:473fd283a090d3546e93915adacf00c69a23ff615c95c968c4a40e8723985853 AS toybox-build
+COPY . .
+ENV FILES="ls tar sh find sha1sum"
+# 0.7.2
+ENV LDFLAGS=--static
+RUN git clone https://github.com/landley/toybox.git && \
+  cd toybox && git checkout b27d5d9ad0c56014d8661d91f69ee498bbbe4cf9 && \
+  make defconfig
+WORKDIR /toybox
+RUN make ${FILES}
+RUN mkdir -p /out/bin
+RUN cp ${FILES} /out/bin
+
+FROM scratch
+ENTRYPOINT []
+CMD []
+WORKDIR /
+COPY --from=toybox-build out/bin bin/

tools/toybox-media/Makefile

@@ -0,0 +1,26 @@
+.PHONY: tag push
+default: push
+
+IMAGE=toybox-media
+SHA_IMAGE=alpine:3.5@sha256:dfbd4a3a8ebca874ebd2474f044a0b33600d4523d03b0df76e5c5986cb02d7e8
+DEPS=Dockerfile Makefile
+
+hash: $(DEPS)
+	find $^ -type f | xargs cat | docker run --rm -i $(SHA_IMAGE) sha1sum - | sed 's/ .*//' > hash
+
+tag: hash
+	docker pull linuxkit/$(IMAGE):$(shell cat hash) || \
+		(docker build --no-cache -t $(IMAGE):build . && \
+		 docker tag $(IMAGE):build linuxkit/$(IMAGE):$(shell cat hash))
+
+push: tag
+	docker pull linuxkit/$(IMAGE):$(shell cat hash) || \
+		docker push linuxkit/$(IMAGE):$(shell cat hash)
+	rm -f hash
+	docker rmi $(IMAGE):build || true
+
+clean:
+	rm -f hash
+	docker rmi $(IMAGE):build || true
+
+.DELETE_ON_ERROR:

tools/toybox-media/README.md

@@ -0,0 +1,3 @@
+`linuxkit/toybox-media` is a small container image, which can be use
+to distribute other files in. It contains a basic shell, `tar`, `ls`,
+`find`, and `sha1sum`. It's compiled from [toybox](https://github.com/landley/toybox.git).