Containerize binfmt_misc

- statically make containerd symlinks so rootfs can be read only
- run binfmt_misc in a containerd container
- ship arm, aarch64, ppc64le qemu static versions that always "just work" as this is supported in Linux 4.8

fix #53

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

alpine/base/qemu-user-static/Dockerfile

@@ -0,0 +1,3 @@
+FROM debian:testing
+
+RUN apt-get update && apt-get -y upgrade && apt-get install -y qemu-user-static

alpine/base/qemu-user-static/Makefile

@@ -0,0 +1,29 @@
+.PHONY: tag push
+
+BASE=debian:testing
+IMAGE=qemu-user-static
+
+default: push
+
+hash: Dockerfile
+	docker pull $(BASE)
+	tar cf - $^ | docker build --no-cache -t $(IMAGE):build -
+	docker run --rm $(IMAGE):build sh -c 'apt list --installed 2>/dev/null | sha1sum' | sed 's/ .*//' > hash
+
+push: hash
+	docker pull mobylinux/$(IMAGE):$(shell cat hash) || \
+		(docker tag $(IMAGE):build mobylinux/$(IMAGE):$(shell cat hash) && \
+		 docker push mobylinux/$(IMAGE):$(shell cat hash))
+	docker rmi $(IMAGE):build
+	rm -f hash
+
+tag: hash
+	docker pull mobylinux/$(IMAGE):$(shell cat hash) || \
+		docker tag $(IMAGE):build mobylinux/$(IMAGE):$(shell cat hash)
+	docker rmi $(IMAGE):build
+	rm -f hash
+
+clean:
+	rm -f hash
+
+.DELETE_ON_ERROR: