WIP: run buildah bud tests using podman

Set of scripts to run buildah's bud.bats test using
podman build in podman CI.

podman build is not 100% compatible with buildah bud.
In particular:

  * podman defaults to --layers=true; buildah to false
  * podman defaults to --force-rm=true; buildah to false
  * podman error exit status is 125; buildah is 2
  * differences in error messages, command-line arguments

Some of the above can be dealt with programmatically,
by tweaking the buildah helpers.bash (BATS helpers).
Some need to be tweaked by patching bud.bats itself.
This PR includes a patch that will, I fear, need to
be periodically maintained over time.

There will likely be failures when vendoring in a
new buildah, possibly because new tests were added
for new features that don't exist in podman, possibly
(I hope unlikely) if existing tests are changed in
ways that make the patch file fail to apply. I've
tried to write good instructions and to write the run
script in such a way that it will offer helpful hints
on failure. My instructions and code will be imperfect;
I hope they will be good enough to merit continued use
of this test (possibly with improvements to the instructions
as we learn more about real-world failures).

Signed-off-by: Ed Santiago <santiago@redhat.com>

.cirrus.yml

@@ -579,6 +579,29 @@ remote_system_test_task:
         TEST_FLAVOR: sys
         PODBIN_NAME: remote
 
+buildah_bud_test_task:
+    name: *std_name_fmt
+    alias: buildah_bud_test
+    skip: *tags
+    only_if: *not_docs
+    depends_on:
+      - local_integration_test
+    env:
+        TEST_FLAVOR: bud
+        DISTRO_NV: ${FEDORA_NAME}
+        # Not used here, is used in other tasks
+        VM_IMAGE_NAME: ${FEDORA_CACHE_IMAGE_NAME}
+        CTR_FQIN: ${FEDORA_CONTAINER_FQIN}
+        # ID for re-use of build output
+        _BUILD_CACHE_HANDLE: ${FEDORA_NAME}-build-${CIRRUS_BUILD_ID}
+        PODBIN_NAME: podman
+    gce_instance: *standardvm
+    timeout_in: 45m
+    clone_script: *noop
+    gopath_cache: *ro_gopath_cache
+    setup_script: *setup
+    main_script: *main
+    always: *int_logs_artifacts
 
 rootless_system_test_task:
     name: *std_name_fmt
@@ -687,6 +710,7 @@ success_task:
         - remote_system_test
         - rootless_system_test
         - upgrade_test
+        - buildah_bud_test
         - meta
     container: *smallcontainer
     env: