There is an updated pull request by q66 against master on the void-packages repository

https://github.com/void-power/void-packages libunwind
https://github.com/void-linux/void-packages/pull/12360

libunwind: add patches for ppc*-musl
Requires https://github.com/void-linux/void-packages/pull/12359 first

This patches some internal bits to compile on ppc(64) with musl, where some structures have a different layout.

A patch file from https://github.com/void-linux/void-packages/pull/12360.patch is attached