Add support for buildd derived images

.gitlab-ci.yml

@@ -14,6 +14,7 @@ services:
 stages:
   - migrate
   - build
+  - derive
 
 before_script:
 - docker login -u gitlab-ci-token -p "$CI_JOB_TOKEN" registry.gitlab.com
@@ -43,3 +44,14 @@ build:
     && docker push "$CI_REGISTRY_IMAGE":"$version"
     && docker tag  "$CI_REGISTRY_IMAGE":"$version" "$CI_REGISTRY_IMAGE"
     && docker push "$CI_REGISTRY_IMAGE"
+
+derive:
+  stage: derive
+  script:
+  - docker build --build_arg DEVUAN_VERSION="$DEVUAN_VERSION"
+           --tag "$CI_REGISTRY_NAME"/buildd:"$DEVUAN_VERSION"
+           --file buildd.df
+  - docker push "$CI_REGISTRY_IMAGE"/buildd:"$DEVUAN_VERSION"
+  - docker tag  "$CI_REGISTRY_IMAGE"/buildd:"$DEVUAN_VERSION"
+                "$CI_REGISTRY_IMAGE"/buildd
+  - docker push "$CI_REGISTRY_IMAGE"/buildd

buildd.df

@@ -0,0 +1,11 @@
+# buildd.df -- a Devuan image for binary package builds
+# Copyright (C) 2017  Olaf Meeuwissen
+#
+# License: GPL-3.0+
+
+ARG   DEVUAN_VERSION
+FROM  devuan:${DEVUAN_VERSION}
+LABEL maintainer="Olaf Meeuwissen <paddy-hack@member.fsf.org>"
+
+RUN apt-get update -q \
+    && apt-get install build-essential -q -y