[llvm] [infra] Add git to Linux container (PR #82687)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

The failure in the stage2 container build is transient (or at least it was in the past). In the past I've been able to resolve it by just rerunning the stage2 job, but in this case that doesn't seem to work. I need to do some investigation there, but it's not super trivial to do experimentation given the total job sequence takes ~8 hours on the self-hosted github runners at this point.

https://github.com/llvm/llvm-project/pull/82687