ci: Run documentation generation in `pages`

As `pages` will be the only job public CI executes, run the commands
to generate the documentation in this job.

Signed-off-by: Saheer Babu <saheer.babu@arm.com>

.gitlab-ci.yml

@@ -223,6 +223,17 @@ pages:
     - iotmsw-amd64
   image: python:latest
   script:
+    - |
+      missing_listing=0
+      for page in `find docs -name "*.md" -exec realpath --relative-to docs {} \;`; do
+        if ! grep -q $page mkdocs.yml; then
+            echo "$page is not listed in mkdocs.yml"
+            missing_listing=1
+        fi
+      done
+      if [ $missing_listing = 1 ]; then exit 1; fi
+    - pip install mkdocs-material lxml GitPython
+    - mkdocs build --site-dir docs_site
     - mv docs_site public
   artifacts:
     paths: