add a deb package for pass/secret service backends

Note that this single source package produces two binary packages: one for
-pass, and one for -secretservice, so that users can install whichever
password backend (and thus deps) that they want.

Signed-off-by: Tycho Andersen <tycho@docker.com>

deb/Dockerfile

@@ -0,0 +1,19 @@
+FROM ubuntu:xenial
+
+ARG VERSION
+ARG DISTRO
+
+RUN apt-get update && apt-get install -yy debhelper dh-make golang-go libsecret-1-dev
+RUN mkdir -p /build
+
+WORKDIR /build
+ENV GOPATH /build
+
+COPY Makefile .
+COPY credentials credentials
+COPY secretservice secretservice
+COPY pass pass
+COPY deb/debian ./debian
+COPY deb/build-deb .
+
+RUN /build/build-deb ${VERSION} ${DISTRO}