[PRQ#48259] Deletion Request for compiler-rt8

MarsSeed [1] filed a deletion request for compiler-rt8 [2]: Legacy package for a version from 2019. Conflicts with repo's compiler-rt. It is not a drop-in replacement. Therefore this is not allowed to be kept on AUR as per submission guidelines. Safe to delete: nothing requires this build apart from its corresponding clang8, submitted for deletion as well (PRQ#48258). [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/compiler-rt8/