[clang] [llvm] [clang-format] Add CI check confirming ClangFormatStyleOptions.rst is up-to-date. (PR #111513)

[Iuri Chaer via cfe-commits]

ichaer wrote:

> IMO it would be more helpful to add the build target to lib/Format/CMakeLists.txt instead. For example,
```
$ ninja FormatTests
```

Moving the target from `clang/docs/CMakeLists.txt` to `lib/Format/CMakeLists.txt` sounds great to me, but the testing part of the thing relies on us being in a `git clone`, it's a very CI-oriented thing, my impression is that it's more appropriate for it to live in the workflow yaml files. I'm saying this because you suggested `FormatTests` as the name... I'm not sure if `clang-format-style-options` is a good name, but I think it's closer to what we can do there. What do you think?

> I'm ok with not adding the CI check though.

IMO that would be sad, I would really like to free maintainers up from having to remember this dependency themselves. Is this because you feel `.github/workflows/docs.yml` is the wrong place for that validation? I see that step more as a pre-build validation for docs than as a test, that's why `docs.yml` looks like a good home for it from my point of view, but we could move it elsewhere if you're uncomfortable with that.



https://github.com/llvm/llvm-project/pull/111513