[CI] Run unit tests

[FabioBatSilva]

Few things going on here:

• add github action to runs unit tests on push
• fix the make file that downloads gtest
• cleanup some warnings/errors on the existing tests

You can see the pipeline running here: https://github.com/FabioBatSilva/vesc-bldc/actions/runs/2184912510 https://github.com/FabioBatSilva/vesc-bldc/pull/1

I believe actions is enable by default.. So it should run after this gets merged unless the configs for the repo have it disabled. https://docs.github.com/en/enterprise-server@3.1/repositories/managing-your-repositorys-settings-and-features/enabling-features-for-your-repository/managing-github-actions-settings-for-a-repository#managing-github-actions-permissions-for-your-repository

see: https://docs.github.com/en/actions

[rusefillc]

@vedderb this looks to be an amazing process improvement do you have time to move this forward?

[rusefillc]

See also https://github.com/vedderb/bldc/pull/167