[llvm] [CI] Add --succinct to lit args (PR #152335)

[David Spickett via llvm-commits]

https://github.com/DavidSpickett approved this pull request.

> Having a progress indicator from lit that works in CI cases is on my TODO list.

https://llvm.org/docs/CommandGuide/lit.html#cmdoption-lit-s

"Also show a progress bar, unless --no-progress-bar is specified."

In CI systems I've used, the progress bar was usually ok while the log was being watched live, but in the final file it would be a lot of:
```
=
==
===
====
```
etc.

I don't know how well it works on GitHub but will be interested to see what you come up with.

> For the rare cases where someone does need to see the list of tests that run, the JUnit XML emitted by lit is available in the artifacts.

I find myself in a lot of those rare cases, and this is fine with me. If it's somehow not enough, we can always patch the script in the same PR.

https://github.com/llvm/llvm-project/pull/152335