Fixes for local ARM development

[robbycochran]

Description

Wire up PLATFORM for building and running tests using non-x86 images.

Checklist

• [ ] Investigated and inspected CI test results
• [ ] Updated documentation accordingly

Automated testing

• [ ] Added unit tests
• [ ] Added integration tests
• [ ] Added regression tests

If any of these don't apply, please comment below.

Testing Performed

TODO(replace-me) Use this space to explain how you tested your PR, or, if you didn't test it, why you did not do so. (Valid reasons include "CI is sufficient" or "No testable changes") In addition to reviewing your code, reviewers must also review your testing instructions, and make sure they are sufficient.

For more details, ref the Confluence page about this section.