Add dockerfile-pre image for preliminary_checks jobs

.gitlab-ci.yml

@@ -24,6 +24,16 @@ build-guix:
     - docker push $CI_REGISTRY_IMAGE/guix
   extends: .config
 
+build-pre:
+  stage: build-first-layout
+  rules:
+    - changes:
+        - dockerfile-pre
+  script:
+    - docker build -f dockerfile-pre -t $CI_REGISTRY_IMAGE/pre . | tee build.log
+    - docker push $CI_REGISTRY_IMAGE/pre
+  extends: .config
+
 build-base:
   stage: build-first-layout
   rules:

dockerfile-pre

+FROM alpine
+
+# install curl and git
+RUN apk add --update bash curl git
+
+# Create a group and user
+RUN addgroup -S gitlab && adduser -S gitlab -G gitlab
+
+# Create a directory where ci jobs are performed
+RUN mkdir /builds && \
+    chown -R gitlab:gitlab /builds && \
+    chmod g+s /builds
+
+# default user
+USER gitlab
+
+# default working directory
+WORKDIR /builds