add Dockerfile

This commit adds a Dockerfile that can be build using podman or docker.

Dockerfile

@@ -0,0 +1,33 @@
+# 1) use alpine to generate a void environment
+FROM alpine:3.9 as stage0
+ARG REPOSITORY=https://alpha.de.repo.voidlinux.org/current
+ARG ARCH=x86_64
+COPY keys/* /target/var/db/xbps/keys/
+RUN apk add ca-certificates && \
+  wget -O - https://alpha.de.repo.voidlinux.org/static/xbps-static-latest.$(uname -m)-musl.tar.xz | \
+    tar Jx && \
+  XBPS_ARCH=${ARCH} xbps-install.static -yMU \
+    --repository=${REPOSITORY} \
+    --repository=${REPOSITORY}/musl \
+    -r /target \
+    base-minimal
+
+# 2) using void to generate the final build
+FROM scratch as stage1
+ARG REPOSITORY=https://alpha.de.repo.voidlinux.org/current
+ARG ARCH=x86_64
+COPY --from=stage0 /target /
+COPY keys/* /target/var/db/xbps/keys/
+RUN xbps-reconfigure -a && \
+  mkdir -p /target/var/cache && ln -s /var/cache/xbps /target/var/cache/xbps && \
+  XBPS_ARCH=${ARCH} xbps-install -yMU \
+    --repository=${REPOSITORY} \
+    --repository=${REPOSITORY}/musl \
+    -r /target \
+    base-minimal
+
+# 3) configure and clean up the final image
+FROM scratch
+COPY --from=stage1 /target /
+RUN xbps-reconfigure -a && \
+  rm -r /var/cache/xbps