boehm-gc: remove sys_select patch

[dylex]

Motivation for this change

This boehm-gc patch referenced a live git repo, from which the patch was removed in
https://gitweb.gentoo.org/proj/musl.git/commit/dev-libs?id=ea1d7393a2fc76acc9fa4f1cd5b8d88590a3a4eb
This adds a fixed hash reference to the origin of this patch. However, given the triviality of this patch, it might make more sense to include it directly. It's also possible the patch is no longer necessary (I haven't tried, yet).

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

---

[alyssais]

The patch is indeed no longer necessary, as far as I can tell, hence it’s removal from Gentoo. You beat me to a PR, but I’ve been using an unpatched version for a few days now.

Could you please remove the patch and change the base of this PR to staging?

[dylex]

It looks like @veprbl instead made my original change in ac7f4c0. Not sure if you still want to remove it instead.

[alyssais]

Still worth removing IMO.

[alyssais]

Side note: GitHub doesn't produce notifications for force pushes, so I didn't get a notification that this PR had been updated. A simple "done" comment is nice in this case to let people following know that something has changed.

[dtzWill]

LGTM!

[alyssais]

Sorted out the merge conflict myself here just to get it over the line.