Fix #853, Use Cache to Avoid Duplicate Workflow Steps

[arielswalker]

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Describe the contribution Fixes #853

Testing performed RTEMS 4.11 RTEMS 5

Expected behavior changes The RTEMS workflows should not checkout code, prep, and make twice for the Build and Test jobs. Instead it should perform those steps once in Build job and cache it for the Test job.

System(s) tested on GitHub Actions

Contributor Info - All information REQUIRED for consideration of pull request Ariel Walker, MCSG TECH.