[clang] [AIX]Fix StaticDiagInfoRec size assertion on AIX (PR #231576)

[Hubert Tong via cfe-commits]

https://github.com/hubert-reinterpretcast commented:

@midhuncodes7, please update the PR description to explain the precedent being followed for the fix, e.g, 844a02e509a4c.

https://github.com/llvm/llvm-project/pull/231576