Use Caching to Speed Up GitHub Actions Builds

[DerekRoberts]

Describe the task Cache build artifacts to save time pulling them down. https://help.github.com/en/actions/configuring-and-managing-workflows/caching-dependencies-to-speed-up-workflows

Acceptance Criteria

• [ ] Appropriate steps are sped up
• [ ] Caching only for public, no security-required portions