Update build and notarize scripts

[twangboy]

What does this PR do?

Improvements to the MacOS build scripts to match those made on the salt-pkg repo.

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• [ ] Docs
• [ ] Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• [ ] Tests written/updated

Commits signed with GPG?

Yes