[clang-tools-extra] [clang-tidy] new check readability-mark-static (PR #90830)

[Danny Mösch via cfe-commits]

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@@ -0,0 +1,26 @@
+.. title:: clang-tidy - readability-unnecessary-external-linkage
+
+readability-unnecessary-external-linkage
+========================================
+
+Detects variable and function can be marked as static.
+
+Static functions and variables are scoped to a single file. Marking functions
+and variables as static helps to better remove dead code. In addition, it gives
+the compiler more information and can help compiler make more aggressive
+optimizations.
----------------
SimplyDanny wrote:

```suggestion
the compiler more information and allows for more aggressive optimizations.
```

https://github.com/llvm/llvm-project/pull/90830