Add scripts for building images manually

Makefile

+DHALL ?= dhall
+gitlab-pipeline.yaml: gitlab-pipeline.dhall
+	${DHALL} text --file=$< > $@
+
+dockerfiles: dockerfiles.dhall
+	mkdir -p dockerfiles
+	${DHALL} to-directory-tree --file=$< --output=$@
+

build-all.sh

+#!/usr/bin/env bash
+
+set -e
+
+commit="$(git rev-parse HEAD)"
+images="$@"
+dhall to-directory-tree --output dockerfiles < dockerfiles.dhall
+if [ -z "$images" ]; then
+    cd dockerfiles
+    images="$(ls)"
+fi
+
+for d in $images; do
+  tag="registry.gitlab.haskell.org/ghc/ci-images/$(basename $d):$commit"
+  docker build -t "$tag" "$d"
+  docker push "$tag"
+done