[llvm] [libc++] Add Docker images to support incoming pre-merge CI transition (PR #144597)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> Ack. I will say though that the inability for folks to see which Docker image we're using in the CI by just looking at the monorepo is a major usability and discoverability issue IMO. I don't want to slow down this migration by requesting a change at this time, but I would like us to revisit this once it is rolled out.

Sounds good. I can look at putting up a PR/writing up an RFC (if needed) to move things over to the monorepo once I start work again (7/7/25).

https://github.com/llvm/llvm-project/pull/144597