Fix release pipeline to handle #1122

Since #1122, we do not treat outputs that were inputs as well in any
special way, meaning that the output folder will be empty unless we
copy the input to the output.

Fix the release pipeline to handle that.

tekton/README.md

@@ -117,7 +117,7 @@ To use [`tkn`](https://github.com/tektoncd/cli) to run the `publish-tekton-pipel
 		--resource=builtWebhookImage=webhook-image \
 		--resource=builtDigestExporterImage=digest-exporter-image \
 		--resource=builtPullRequestInitImage=pull-request-init-image \
-    --resource=builtGcsFetcherImage=gcs-fetcher-image \
+                --resource=builtGcsFetcherImage=gcs-fetcher-image \
 		pipeline-release
    ```