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

https://github.com/Piraty/void-packages dkms-modpost-fix
https://github.com/void-linux/void-packages/pull/24846

dkms: build modpost
see https://github.com/void-linux/void-packages/pull/24449#issuecomment-683459462

Tested on:
* aarch64-musl, rpi-kernel-headers-5.4.59_1

A patch file from https://github.com/void-linux/void-packages/pull/24846.patch is attached