ci: Place container storage inside work volume

This commit updates the CI workflow to explicitly configure the Podman
container storage to be inside the runner work volume (`__w`), which is
guaranteed to have at least 100GB available.

The default container storage path is `/var/lib/containers/storage`,
which resides in the Docker storage volume that has no free space
guarantees.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

.github/workflows/ci.yml

@@ -46,6 +46,11 @@ jobs:
           builder: zephyr-runner-v2-linux-arm64-4xlarge
 
     steps:
+    - name: Configure container storage
+      run: |
+        sed -i 's/graphroot = .*/graphroot = "\/__w\/container_storage"/' /etc/containers/storage.conf
+        mkdir -p /__w/container_storage
+
     - name: Checkout
       uses: actions/checkout@v4