Remove "set-output" usage in GitHub action

[jmini]

When the GitHub actions are executed we see this warning:

Build JDK 8
The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

This PR is fixing that by using the the new way of setting outputs.

See:
https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-of-setting-an-output-parameter