[clang] [Clang] Fix preserved C++ field indices (PR #226790)

[Tamir Duberstein via cfe-commits]

tamird wrote:

This was extracted while reviewing #226717 to separate the Clang producer fix from BTF’s handling of C++ record elements. The intrinsic contract is unchanged, and the producer correction can be reviewed independently of the backend changes.

Assisted-by: OpenAI Codex


https://github.com/llvm/llvm-project/pull/226790