Cirrus: Allow manually running image-build task

Building multi-arch images in a standardized way is complex.  Some
of the builds themselves can take a really long time to run (over
an hour).  Make changes easier to test inside a PR by adding
manually-triggered image-build tasks.  These mirror most of the real
cron-triggered task, without actually pushing the final images.

Signed-off-by: Chris Evich <cevich@redhat.com>

.cirrus.yml

@@ -741,7 +741,7 @@ upgrade_test_task:
     always: *logs_artifacts
 
 
-image_build_task:
+image_build_task: &image-build
     name: "Build multi-arch $CTXDIR"
     alias: image_build
     # Some of these container images take > 1h to build, limit
@@ -774,6 +774,18 @@ image_build_task:
         - main.sh $CIRRUS_REPO_CLONE_URL $CTXDIR
 
 
+test_image_build_task:
+    <<: *image-build
+    # Allow this to run inside a PR
+    only_if: $CI == $CI
+    # This takes a LONG time, only run when requested.  N/B: Any task
+    # made to depend on this one will block FOREVER unless triggered.
+    trigger_type: manual
+    # Overwrite all 'env', don't push anything, just do the build.
+    env:
+        DRYRUN: 1
+
+
 # This task is critical.  It updates the "last-used by" timestamp stored
 # in metadata for all VM images.  This mechanism functions in tandem with
 # an out-of-band pruning operation to remove disused VM images.

contrib/cirrus/cirrus_yaml_test.py

@@ -26,7 +26,8 @@ class TestCaseBase(unittest.TestCase):
 class TestDependsOn(TestCaseBase):
 
     ALL_TASK_NAMES = None
-    SUCCESS_DEPS_EXCLUDE = set(['success', 'artifacts', 'release', 'release_test'])
+    SUCCESS_DEPS_EXCLUDE = set(['success', 'artifacts',
+        'test_image_build', 'release', 'release_test'])
 
     def setUp(self):
         super().setUp()