[PRQ#39532] Merge Request for isl15

tallero [1] filed a request to merge isl15 [2] into libisl15 [3]: I have added the updated name and parameterized the recipe. [1] https://aur.archlinux.org/account/tallero/ [2] https://aur.archlinux.org/pkgbase/isl15/ [3] https://aur.archlinux.org/pkgbase/libisl15/