Add CI after setting variables and permissions

.gitignore

+*latest_updates.md
+*monthly_updates.md
+docs/sitemap/*

.gitlab-ci.yml

+stages:
+  - build
+
+.prod_variables: &prod_variables
+  OC_OPTIONS: --token ${LINUXARCHIVE_OPENSHIFT} --server https://openshift.cern.ch --namespace linux-archive
+
+.common_functions: &common_functions |
+  # redefine oc to use the appropriate options. alias doesn't work here: https://askubuntu.com/a/98786
+  function oc {
+    /bin/oc $OC_OPTIONS "$@"
+  }
+
+.common_script: &common_script |
+  oc start-build linux-archive --wait
+
+build_prod:
+  stage: build
+  image: gitlab-registry.cern.ch/paas-tools/openshift-client
+  before_script:
+    - *common_functions
+  script:
+    - *common_script
+  variables:
+    <<: *prod_variables
+  only:
+    - master