Check out repo with submodules

Author: ogenstad

.github/workflows/ci.yml

@@ -570,7 +570,9 @@ jobs:
       group: huge-runners
     steps:
       - name: Check out repository code
-        uses: actions/checkout@v4
+        uses: "actions/checkout@v5"
+        with:
+          submodules: true
       - name: Set up Python
         id: python
         uses: actions/setup-python@v6