[libc-commits] [libc] [libc][NFC] Fix few warnings in tests. (PR #81262)

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lntue wrote:

> In the future, consider putting the text of the warning in the commit message. This helps reviewers track what kinds of diagnostics you are addressing.

Updated the PR description to include the warning messages for future reference.

https://github.com/llvm/llvm-project/pull/81262