New review comment by ahesford on void-packages repository

https://github.com/void-linux/void-packages/pull/37139#discussion_r874748318

Comment:
Just keep the version we have in `$FILESDIR`. Our script is a bit more verbose (listing the kernel package name) and explicitly calling `/usr/bin/dkms` is better than calling `dkms` when the script verifies that the former exists but the latter is subject to `$PATH` shenanigans.

This will also make the script less likely to subtly break in a future update if there are unnoticed changes.