Update Docker build for new mirage-xen

Also, switched to the experimental new OCurrent images, as they are much
smaller:

- Before: 1 GB (ocaml/opam2:debian-10-ocaml-4.08)
- Now:  309 MB (ocurrent/opam:alpine-3.10-ocaml-4.08)

.dockerignore

@@ -2,3 +2,6 @@
 _build
 *.xen
 *.bz2
+*.tar.bz2
+*.tgz
+mirage-firewall-bin*

Dockerfile

@@ -1,16 +1,15 @@
 # Pin the base image to a specific hash for maximum reproducibility.
 # It will probably still work on newer images, though, unless Debian
 # changes some compiler optimisations (unlikely).
-#FROM ocaml/opam2:debian-9-ocaml-4.07
-FROM ocaml/opam2@sha256:74fb6e30a95e1569db755b3c061970a8270dfc281c4e69bffe2cf9905d356b38
+#FROM ocurrent/opam:alpine-3.10-ocaml-4.08
+FROM ocurrent/opam@sha256:4cf6f8a427e7f65a250cd5dbc9f5069e8f8213467376af5136bf67a21d39d6ec
 
 # Pin last known-good version for reproducible builds.
 # Remove this line (and the base image pin above) if you want to test with the
 # latest versions.
-RUN git fetch origin && git reset --hard 3389beb33b37da54c9f5a41f19291883dfb59bfb && opam update
+RUN cd ~/opam-repository && git fetch origin master && git reset --hard a83bd077e4e54c41b0664a2e1618670d57b7c79d && opam update
 
-RUN sudo apt-get install -y m4 libxen-dev pkg-config
-RUN opam install -y mirage lwt
+RUN opam depext -i -y mirage lwt
 RUN mkdir /home/opam/qubes-mirage-firewall
 ADD config.ml /home/opam/qubes-mirage-firewall/config.ml
 WORKDIR /home/opam/qubes-mirage-firewall

build-with-docker.sh

@@ -5,5 +5,5 @@ docker build -t qubes-mirage-firewall .
 echo Building Firewall...
 docker run --rm -i -v `pwd`:/home/opam/qubes-mirage-firewall qubes-mirage-firewall
 echo "SHA2 of build:   $(sha256sum qubes_firewall.xen)"
-echo "SHA2 last known: 5707d97d78eb54cad9bade5322c197d8b3706335aa277ccad31fceac564f3319"
+echo "SHA2 last known: 3cf9358df911c7bc5a28846087c5359e5b550e5d0c6cf342a6e1c90545518ac6"
 echo "(hashes should match for released versions)"

config.ml

@@ -33,6 +33,7 @@ let main =
       package "mirage-qubes";
       package "mirage-nat" ~min:"1.2.0";
       package "mirage-logs";
+      package "mirage-xen" ~min:"4.0.0";
     ]
     "Unikernel.Main" (mclock @-> job)