[llvm] Make update_any_test_check.py script accepting @listfile CL argument. (PR #86800)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

Please do take a look at the formatting complaint.

Is their precedent somewhere for using the '@' as a prefix in this way? Seems a bit unorthodox to me. Perhaps because a more "CLI idiomatic" way of achieving the same thing is to just run something like `cat yourfile | xargs update_any_test_checks.py`.

https://github.com/llvm/llvm-project/pull/86800