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

https://github.com/stenstorp/void-packages qt5-webkit
https://github.com/void-linux/void-packages/pull/12049

qt5-webkit: Fix building on ppc
Cmake expects CMAKE_SYSTEM_PROCESSOR to be set to "ppc" when it should be "powerpc".
Also use -latomic and disable JIT.

A patch file from https://github.com/void-linux/void-packages/pull/12049.patch is attached