[llvm] workflows: Rewrite build-ci-container to work on larger runners (PR #117353)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> It looks like thellvm-premerge-linux-runners require jobs to use a container and having nested containers doesn't work, so I may have to switch it back to the depot runners.

Ah, right. I forgot about that detail. My plan was to use https://github.com/GoogleContainerTools/kaniko to build things on the cluster, but that's definitely something I can get to later.

https://github.com/llvm/llvm-project/pull/117353