New review comment by tornaria on void-packages repository

https://github.com/void-linux/void-packages/pull/33332#discussion_r725649409

Comment:
- `pkgname=isl`: because that's the right thing to do, otherwise update-check doesn't find anything.
- `ignore=*`: because this pkg is only used as a dependency for cross gcc so its update is tied to those pkgs. My rationale is: if it isn't going to be updated based on its current version, then it shouldn't be listed as updatable.

Having an empty update file or only `ignore=*`  results in update-check complaining `NO VERSION found for isl15`.

Do you know why gcc and cross-* don't use the latest version of isl?