[clang] [clang][python] Make .git_archival.txt deterministic. (PR #223362)

[Aiden Grossman via cfe-commits]

boomanaiden154 wrote:

> I am curious though why the downstream projects are referencing commits that don't correspond to a release tag, since commits corresponding to release tags just use the tag as the describe-name and won't change over time.

We live near Tip of Tree (typically trailing by < 7 days) and update very frequently (ideally multiple times a week).

https://github.com/llvm/llvm-project/pull/223362