[llvm] [NFC][CodingStandard] Require``[[maybe_unused]]`` for unused variables in asserts (PR #142850)

[James Henderson via llvm-commits]

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@@ -591,6 +591,8 @@ rather than C-style casts. There are two exceptions to this:
 
 * When casting to ``void`` to suppress warnings about unused variables (as an
   alternative to ``[[maybe_unused]]``). Prefer C-style casts in this instance.
+  Note that if the variable is unused because its used only in ``assert``, use
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jh7370 wrote:

```suggestion
  Note that if the variable is unused because it's used only in ``assert``, use
```

https://github.com/llvm/llvm-project/pull/142850