Accommodate set-env deprecation announcement about macpro-quickstart-serverless HOT 1 CLOSED

I took a quick look at this. https://docs.github.com/en/free-pro-team@latest/actions/reference/workflow-commands-for-github-actions#environment-files

It looks like github has moved to something very similiar to circleci. You can echo variable key value pairs into a file, and that file is sourced for all steps. So in circle ci you can echo stuff into $BASH_ENV and it looks like here you can echo into $GITHUB_ENV

If that's the case, this should be simple to implement.

The most critical piece by far is to fully understand the masking behavior, especially with regards to our per-branch variable override strategy

from macpro-quickstart-serverless.