There is a new pull request by pullmoll against master on the void-packages repository

https://github.com/pullmoll/void-packages yaboot
https://github.com/void-linux/void-packages/pull/25038

yaboot: fix build w/ gcc10 and host i686/x86_64
The -fcommon is required for gcc10 to build yaboot.
Adding --build=$XBPS_TRIPLET seems to be a good idea in any case
according to the autoconf manual, see the document at:
https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Hosts-and-Cross_002dCompilation.html

Still gives an error for me trying to build for ppc-musl using any
x86 host environment, be it glibc or musl libc.

More patches required or something else may be wrong?

A patch file from https://github.com/void-linux/void-packages/pull/25038.patch is attached