GitHub actions `build` should test on `aarch` self hosted runners

[jpmcb]

What I expected to happen:

When the build GitHub action runs, it has a matrix strategy that incorporates different architecture builds (i.e. x86_64 and aarch)

https://github.com/bottlerocket-os/bottlerocket/blob/64708022dea79f6e7c21545d8cb016f45af304be/.github/workflows/build.yml#L28

Given the architecture is apart of the Action's strategy for testing Bottlerocket, I'd expect the tests and builds to also run ontop of the corresponding machine.

What actually happened:

It appears, as evidenced by https://github.com/bottlerocket-os/bottlerocket/issues/2360, that this is not the case. The self hosted runners must be x86_64 machines that also cross build to the target architecture with the matrix.arch argument:

https://github.com/bottlerocket-os/bottlerocket/blob/64708022dea79f6e7c21545d8cb016f45af304be/.github/workflows/build.yml#L122-L123

Instead, we should consider adding aarch based self hosted runners that can be targeted to run / test / build the aarch variants given the Action's matrix strategy.