[llvm] [libcxx] Add pre-commit hooks and git config for libc++ & git-clang-format. (PR #73798)

[Louis Dionne via llvm-commits]

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@@ -9,16 +9,24 @@ permissions:
 
 jobs:
   check_generated_files:
-    runs-on: ubuntu-latest
+    runs-on:
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ldionne wrote:

I think there's a bit of confusion here. This job doesn't actually check for clang-format anymore. We should just stop installing clang-format in this job, I guess I missed that when we stopped enforcing clang-format via this job.

We exclusively enforce clang-format via the `pr-code-format.yml` workflow now.

https://github.com/llvm/llvm-project/pull/73798