SuperTuxKart: Replaced some bundled libraries with system ones

[SCOTT-HAMILTON]

Motivation for this change

Was packaging WiiUse when noticed
that SuperTuxKart was conflicting with it. So I came with
this partially unbundled build. This should also reduce the package size a bit.

Things done

Replaced some bundled libs with system ones.

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• 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 nixpkgs-review --run "nixpkgs-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)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[SCOTT-HAMILTON]

Needs #91425, waiting for this PR to be merged.

[teto]

cool job using system libraries instead. Could you check the reduction in closure size.
Also I've merged your other PR in case you wanna rebase.

[teto]

why removing the check about USE_IPV6 ?

[SCOTT-HAMILTON]

libenet doesn't yet support ipv6 upstream lsalzman/enet#109.
So I either disable ipv6 or I use the bundled libenet (which has been fixed to support ipv6).

[teto]

ok but instead of patching, you could probably pass USE_IPV6=no https://notabug.org/Supertuxkart/stk-code/src/master/CMakeLists.txt#L32 ? also maybe we could keep using the bundled enet until the next release with ipv6 support otherwise the update removes feature.

[SCOTT-HAMILTON]

In terms of closuze size it's getting worse :
890.0M before against 898.2M now.

I don't really explain this. It doesn't seem to be static linking since all
libs are dynamically linked.

[teto]

maybe the system packages have a bigger closure because they are built with more options/stuff ?

[teto]

the difference is little and if one of the lib is reused, it becomes a gain (again :) ) so not an issue for me.

[SCOTT-HAMILTON]

Since the bundled libs are statically linked, this frees 2M on the final executable :
17M→15M

[SCOTT-HAMILTON]

New rebasing : added WiiUse, removed CMakeLists.txt patch and added libenet to whitelist of bundled libs to keep.

[teto]

if we whitelist enet, then we don't use the system one

[SCOTT-HAMILTON]

Fixed

[teto]

ran nixpkgs-review and... endud up to complete 2 laps with tux. thanks