[release/6.0] Ensure _Dumps artifacts aren't empty

- backport of #36419
- avoid yellow builds due to `PublishBuildArtifacts@1` warnings
- always include a small file

Co-authored-by: Doug Bunting <6431421+dougbu@users.noreply.github.com>

.azure/pipelines/jobs/default-build.yml

@@ -273,7 +273,9 @@ jobs:
       condition: always()
       continueOnError: true
       inputs:
-        contents: '*.core'
+        contents: |
+          '*.core'
+          restore.sh
         sourceFolder: $(System.DefaultWorkingDirectory)
         targetFolder: artifacts/dumps/
     - task: PublishBuildArtifacts@1