Backport PR #11580: Explicitly build JupyterLab in dev-mode (#11585)

.github/workflows/galata.yml

@@ -48,6 +48,8 @@ jobs:
       - name: Install dependencies
         run: |
           bash ./scripts/ci_install.sh
+          # Build dev-mode
+          jlpm run build
 
       - name: Launch JupyterLab
         run: |