Cherry-pick "[libunwind] Avoid a warning in 32 bit builds. NFC." to 14.x

[mstorsjo]

[mstorsjo]

/cherry-pick dfa5ab7

[llvmbot]

/branch llvmbot/llvm-project/issue53685

[llvmbot]

/pull-request llvmbot#27

[mstorsjo]

This actually was manually cherrypicked into the release branch by someone else already, so this cherrypick can be closed.

[tstellar]

Merged: 816988d