Specify buildx driver as normal default, not actions default

.github/workflows/sgdk-docker.yml

@@ -47,6 +47,10 @@ jobs:
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
+        with:
+          # Without this option, an image built by one step is not available
+          # locally for the next step.
+          driver: docker
 
       - name: Create build cache directory
         run: |