Wayland and Weston are now provided by ArchLinux, this means the hawaii repository is not going to provide them anymore.

ArchLinux wiki has more information about it.

Enable testing, extra and community-testing.

Remove previously installed weston-git

First remove weston-git:

pacman -R weston-git

then install cairo, replacing cairo-gl:

pacman -Syu cairo

Remove a previously installed mesa-full-wayland

If you previously installed mesa-full-wayland you have to install mesa from testing:

sudo pacman --needed -Syu mesa libdrm libgl libglapi libegl libgles intel-dri nouveau-dri libgbm khrplatform-devel

Install Wayland and Weston

Now install wayland and weston:

pacman -Syu wayland weston