[sanitizer_common][AIX] Use scoped pragma to suppress atomic alignment warnings (#139272)

Have the warning suppression apply only to the code that is currently
affected. The suppression is guarded via preprocessor conditions to
cases where it is tested and known to be needed.

Issue: https://github.com/llvm/llvm-project/issues/138916

Co-authored-by: Hubert Tong <hubert.reinterpretcast@gmail.com>
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GitOrigin-RevId: 5b2fc2bfb9b8ccc4e3cded7c998c31438d7be5fb
1 file changed