CI - Containerize linux x86_64 GNU builds

[bfops]

Description of Changes

We've been having awful issues with some weird permission denied error with the linux x86_64 GNU builds running on bare metal. We suspect that the alpine builds don't have this issue because they run in a container, so we're making these run in a container too.

API and ABI breaking changes

No. CI-only change.

Expected complexity level and risk

1

Testing

I DON'T KNOW HOW TO FEEL CONFIDENT ABOUT ANYTHING ANYMORE T_T