If someone is interested in just using manjaro’s builds of mesa but with support for patented codecs, they can use this simple script
#!/bin/bash
cd /tmp/
git clone https://gitlab.manjaro.org/packages/extra/mesa.git
cd /tmp/mesa/
sed -i '/-D microsoft-clc=disabled \\/a \ -D video-codecs=vc1dec,h264dec,h264enc,h265dec,h265enc \\' PKGBUILD
makepkg -si
cd /tmp/
rm -Rf mesa
I have no idea what the best way to automate it would be. Would be nice if someone could advise me on that front. If this script could be automated with manjaro’s mesa updates, I would not bother switching to arch (compiling does not take much time when all the files are stored in ram).
Also, probably add all the gpg keys in the PKGBUILD before running it.