[clang] [clang] LazyOffsetPtr: Use native pointer width (PR #111995)

[A. Wilcox via cfe-commits]

awilfox wrote:

> Btw, if you submit a fix, it would be great if it could be backported to the 18 and 19 branches.

I think the 18 branch may already be closed.  This is what we are shipping in Adélie for 18: [big-endian-32.patch](https://github.com/user-attachments/files/17404400/big-endian-32.patch).

https://github.com/llvm/llvm-project/pull/111995