Added Debian Dockerfile.

Dockerfile

+FROM debian:stretch-slim as scratch
+ENV GOSU_VERSION 1.10
+RUN set -ex; \
+	\
+	fetchDeps=' \
+		ca-certificates \
+        dirmngr \
+        gpg \
+        gpg-agent \
+		wget \
+	'; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends $fetchDeps; \
+	rm -rf /var/lib/apt/lists/*; \
+	\
+	dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')"; \
+	wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch"; \
+	wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch.asc"; \
+	\
+# verify the signature
+	export GNUPGHOME="$(mktemp -d)"; \
+	gpg --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4; \
+	gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu; \
+	\
+	chmod +x /usr/local/bin/gosu; \
+# verify that the binary works
+	gosu nobody true;
+
+FROM debian:stretch-slim
+COPY --from=scratch /usr/local/bin/gosu /usr/local/bin/