MarsSeed [1] filed a deletion request for isl14 [2]:
This legacy version from 7+ years ago seems not needed anymore.
Only cloog-isl14 depends on it, but that is not used by anything.
(Submitted deletion request for that.)
So in order to ease maintenance burden, I recommend to delete
this as well, if there are no objections.
(Also, the main isl package has been adopted from AUR
to Arch [core] under the name 'libisl'. So all isl* packages
on AUR should either be renamed in accordance, or deleted if
not used.)
[1] https://aur.archlinux.org/account/MarsSeed/
[2] https://aur.archlinux.org/pkgbase/isl14/