[llvm] [GitHub] Bump clang-tidy version to 21th and add sccache in CI (PR #160551)

[Aiden Grossman via llvm-commits]

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@@ -59,6 +60,13 @@ jobs:
 
       - name: Install Python dependencies
         run: python3 -m pip install -r llvm/utils/git/requirements_linting.txt
+
+      - name: Setup ccache
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boomanaiden154 wrote:

This is not going to give you any caching across PRs due to how the caches are namespaced.

https://github.com/llvm/llvm-project/pull/160551