You can build this iso if you have the right version of Archiso.
Archiso is a package supplied by Arch Linux that will always undergo changes.
You can follow up the versions via this link.
https://www.archlinux.org/packages/extra/any/archiso/
We are now using this version
archiso-version=archiso 58-2
sudo pacman -Q archiso and you will know your version
Downgrade to this version via a command in the terminal if you have a higher version.
sudo downgrade archiso
and choose the right version.
Add it to the ignore list of pacman.
If you have a lower version then update your system. Check to see if archiso is not added to your /etc/pacman.conf in the list of ignores. Delete it if it is in there. Then update.