Streamline CU::RepositoryRegistry.setup-repositories
Streamline CU::RepositoryRegistry.setup-repositories

- part 3
- move initial $next-repo initialization into non-precomp if
  so we need to check that condition one time less

MasterDuke17/rakudo,salortiz/rakudo,nbrown/rakudo,nbrown/rakudo,nbrown/rakudo,nbrown/rakudo,labster/rakudo,rakudo/rakudo,labster/rakudo,tony-o/rakudo,labster/rakudo,MasterDuke17/rakudo,softmoth/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,rakudo/rakudo,labster/rakudo,rakudo/rakudo,tony-o/rakudo,MasterDuke17/rakudo,salortiz/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,salortiz/rakudo,tony-o/rakudo,tbrowder/rakudo,nbrown/rakudo,tbrowder/rakudo,softmoth/rakudo,tbrowder/rakudo,rakudo/rakudo,nbrown/rakudo,salortiz/rakudo,softmoth/rakudo,softmoth/rakudo,tony-o/rakudo,tbrowder/rakudo,tony-o/rakudo,tony-o/rakudo,softmoth/rakudo,rakudo/rakudo,tbrowder/rakudo,tbrowder/rakudo,rakudo/rakudo