[clang] [CIR] Fix warnings related to unused variables in release builds (PR #151412)

[Andy Kaylor via cfe-commits]

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@@ -137,7 +137,7 @@ struct CallArg {
 
   /// A data-flow flag to make sure getRValue and/or copyInto are not
   /// called twice for duplicated IR emission.
-  mutable bool isUsed;
+  [[maybe_unused]] mutable bool isUsed;
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andykaylor wrote:

Ironic, isn't it?

https://github.com/llvm/llvm-project/pull/151412