add build info section in manifest (port changes from PR #111)

[ChongZhou-Broadcom]

Port changes from PR #111 for v2.x/staging

The fix enables the zowe-actions/zlux-builds/plugins/prepare-workflow to generate build information in the manifest.yaml.

[1000TurquoisePogs]

This does not work.
The output produces a manifest which says

build:
  branch: "{{build.branch}}"
  number: "{{build.number}}"
  commitHash: "{{build.commitHash}}"
  timestamp: {{build.timestamp}}

That is, the templates are not filled in.
This is because the github workflow probably does not do anything with that information.

[ChongZhou-Broadcom]

@1000TurquoisePogs Hi, thanks for the comment. I believe it was because the PR-46 for zowe-actions/zlux-builds had not been merged when you observed the problem 3 days ago. I reran the build workflow just now and the new result package has the build information in the manifest.json.