Write docker/config.json for CI Image generation

See gh-24461

ci/tasks/build-ci-image.yml

@@ -13,6 +13,15 @@ caches:
 params:
   CONTEXT: ci-images-git-repo/ci/images
   DOCKERFILE: ci-images-git-repo/ci/images/((ci-image-name))/Dockerfile
-  REGISTRY_MIRRORS: ((dockerhub-registry-mirror))
+  REGISTRY_MIRRORS: ((docker-hub-mirror))
+  DOCKER_HUB_AUTH: ((docker-hub-auth))
 run:
-  path: build
+  path: /bin/sh
+  args:
+  - "-c"
+  - |
+    mkdir -p /root/.docker
+    cat > /root/.docker/config.json <<EOF
+    { "auths": { "https://index.docker.io/v1/": { "auth": "$DOCKER_HUB_AUTH" }}}
+    EOF
+    build