New review comment by TinfoilSubmarine on void-packages repository

https://github.com/void-linux/void-packages/pull/33586#discussion_r735854210

Comment:
Needs to include DESTDIR, something like
```
ln -sf /usr/bin/ffmpeg ${DESTDIR}/usr/bin/ffmpeg_harvid
ln -sf /usr/bin/ffprobe ${DESTDIR}/usr/bin/ffprobe_harvid
```