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

https://github.com/void-ppc/void-packages llvm12-rebuild
https://github.com/void-linux/void-packages/pull/31617

llvm12: clean up template, fix libc++ with compiler-rt
[ci skip]

A patch file from https://github.com/void-linux/void-packages/pull/31617.patch is attached