test: add minimal test for container based building of images

This commit adds a smoke test that builds the ibcli container
and runs a fedora-41 raw-minimal build to double check that
the container based building actually works.

Thanks to Ondrej for suggesting this.

test/containerbuild.py

@@ -0,0 +1,23 @@
+import os
+import platform
+import random
+import string
+import subprocess
+import textwrap
+from contextlib import contextmanager
+
+import pytest
+
+
+# XXX: copied from bib
+@pytest.fixture(name="build_container", scope="session")
+def build_container_fixture():
+    """Build a container from the Containerfile and returns the name"""
+
+    container_tag = "image-builder-cli-test"
+    subprocess.check_call([
+        "podman", "build",
+        "-f", "Containerfile",
+        "-t", container_tag,
+    ])
+    return container_tag