isl: switch to https://libisl.sourceforge.io/ for homepage/tarball url (#86896)
isl: switch to https://libisl.sourceforge.io/ for homepage/tarball url (#86896)

isl.gforge.inria.fr has been shutdown: https://giters.com/coq/opam-coq-archive/issues/1298?amp=1
chrisfinazzo/homebrew-core,uyjulian/homebrew-core,mfikes/homebrew-core,nandub/homebrew-core,stgraber/homebrew-core,Homebrew/homebrew-core,makigumo/homebrew-core,sjackman/homebrew-core,Moisan/homebrew-core,stgraber/homebrew-core,uyjulian/homebrew-core,lemzwerg/homebrew-core,cblecker/homebrew-core,filcab/homebrew-core,chrisfinazzo/homebrew-core,zyedidia/homebrew-core,cblecker/homebrew-core,mfikes/homebrew-core,adam-moss/homebrew-core,Homebrew/homebrew-core,nbari/homebrew-core,makigumo/homebrew-core,lemzwerg/homebrew-core,nbari/homebrew-core,adam-moss/homebrew-core,filcab/homebrew-core,nandub/homebrew-core,zyedidia/homebrew-core,Moisan/homebrew-core,sjackman/homebrew-core