The primus_vk package prior to version 1.3-1 was missing some soname links. This has been fixed in 1.3-1 so the upgrade will need to overwrite the untracked soname links. If you get an error like:
primus_vk: /usr/lib/libnv_vulkan_wrapper.so.1 exists in filesystem
primus_vk: /usr/lib/libprimus_vk.so.1 exists in filesystem
when updating, use:
pacman -Syu --overwrite=/usr/lib/libnv_vulkan_wrapper.so.1,/usr/lib/libprimus_vk.so.1
to perform the upgrade.