Add prune step to CI (#79)

Clear all the podman images/containers as first step in the CI process.

This assumes, we don't have any concurrent SDK CI builds on the machine
that hosts the runner. This holds true, and avoid piling up disk space
for dangling images.

.github/workflows/wkdev-sdk.yml

@@ -26,6 +26,10 @@ jobs:
       - name: Checkout repo
         uses: actions/checkout@v4
 
+      - name: Prune podman containers/images
+        run: |
+          podman system prune --all --force
+
       - name: Build image
         run: |
           source ./register-sdk-on-host.sh