[clang] [Clang] Fix offsetof sign-extending unsigned array indices >= 128 (PR #204139)

[Marlus Cadanus da Costa via cfe-commits]

marlus wrote:

Fixed. The test failures were due to incorrect expected-note annotations and #include <cstdint> not being available with -nostdsysteminc. Both fixed and verified locally.

https://github.com/llvm/llvm-project/pull/204139