pkg: Use tini from alpine base in rngd

This makes the package slightly bigger as tini from Alpine
is not statically linked but removes the dependency on
./tools/tini

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

pkg/rngd/Dockerfile

@@ -1,4 +1,11 @@
-FROM linuxkit/alpine:6336329f15b4166514782eaa555cf0ffd35c519c@sha256:f6c2ce92910b1d6e4e5557850a554f4a3ae9f66c1e89ad86a24d6c6e550f165e AS build
+FROM linuxkit/alpine:dae8bcbc6e2cec0a1cc1958dddbc5d6bd3ccf9a0@sha256:02c251d54c4083a596ead8cae92144306b385db0ff961c95a3a620a4c69961ed AS mirror
+RUN mkdir -p /out/etc/apk && cp -r /etc/apk/* /out/etc/apk/
+RUN apk add --no-cache --initdb -p /out \
+    tini
+RUN rm -rf /out/etc/apk /out/lib/apk /out/var/cache
+RUN mkdir -p /out/dev /out/proc /out/sys
+
+FROM linuxkit/alpine:dae8bcbc6e2cec0a1cc1958dddbc5d6bd3ccf9a0@sha256:02c251d54c4083a596ead8cae92144306b385db0ff961c95a3a620a4c69961ed AS build
 RUN apk add \
     argp-standalone \
     automake \
@@ -28,15 +35,10 @@ RUN cd $pkgname-$pkgver && \
   make && \
   make DESTDIR=/ install && \
   strip /usr/sbin/rngd
-RUN mkdir -p /tmp/dev /tmp/proc /tmp/sys
 
-
-FROM linuxkit/tini:cb32c9b3ceb16505e1d62919cf28c8b52bf6d57e@sha256:1645296b3e155f8cf672f71f8d20b274bf38ee94c39dd1b58f7b18e0163b00b8
+FROM scratch
 ENTRYPOINT []
 WORKDIR /
+COPY --from=mirror /out/ /
 COPY --from=build usr/sbin/rngd usr/sbin/rngd
-# Can't create directories, so copy empty dirs from previous context
-COPY --from=build tmp/dev dev
-COPY --from=build tmp/proc proc
-COPY --from=build tmp/sys sys
-CMD ["/bin/tini", "/usr/sbin/rngd", "-f"]
+CMD ["/sbin/tini", "/usr/sbin/rngd", "-f"]

pkg/rngd/Makefile

@@ -8,7 +8,7 @@ DEPS=Dockerfile
 HASH?=$(shell git ls-tree HEAD -- ../$(notdir $(CURDIR)) | awk '{print $$3}')
 
 tag: $(DEPS)
-	docker build --no-cache -t $(ORG)/$(IMAGE):$(HASH) .
+	docker build --squash --no-cache -t $(ORG)/$(IMAGE):$(HASH) .
 
 push: tag
 	DOCKER_CONTENT_TRUST=1 docker pull $(ORG)/$(IMAGE):$(HASH) || \