flocke  filed a deletion request for arc-themes :
https://aur.archlinux.org/packages/gtk-theme-arc/ provides the same Gtk theme. I must have overlooked it before creating this one.
 https://aur.archlinux.org/account/flocke/  https://aur.archlinux.org/pkgbase/arc-themes/
Request #5190 has been accepted by flocke :
Deletion of a fresh package requested by its current maintainer.