[libunwind] [libunwind] Fix compilation for the x32 ABI. (PR #116608)

[Alex Rønne Petersen via cfe-commits]

alexrp wrote:

CI failure here seems unrelated: https://github.com/llvm/llvm-project/actions/runs/11930420176/job/33253113656?pr=116608

https://github.com/llvm/llvm-project/pull/116608