This is repository is now obsolete. Manjaro is back to the arch version of the mesa packages.

PKGS="$(pacman -Sl mesa-nonfree | grep 'installed' | awk '{print $2}')"
sudo sed -i '/mesa-nonfree/d' /etc/pacman.conf
sudo pacman -Sy $(echo ${PKGS//$'\n'/ })

This builds the latest version available on the arch repository on the manjaro unstable branch. Using it on the unstable channel is thus strictly recommended!