rpcs3: add `USE_SDL` and `USE_DISCORD_RPC` flags

[SuperSamus]

Description of changes

They are enabled in the official builds, so it makes sense to enable them here too. These are enabled unconditionally: tell me if it'd be better to have a useX option for them.

Things done

• Built on platform(s)
  • [x] x86_64-linux
  • [ ] aarch64-linux
  • [ ] x86_64-darwin
  • [ ] aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • [ ] sandbox = relaxed
  • [ ] sandbox = true
• [ ] Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• [ ] Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• [x] Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • [ ] (Package updates) Added a release notes entry if the change is major or breaking
  • [ ] (Module updates) Added a release notes entry if the change is significant
  • [ ] (Module addition) Added a release notes entry if adding a new NixOS module
• [x] Fits CONTRIBUTING.md.

---

Add a :+1: reaction to pull requests you find important.

[vs49688]

@ofborg build rpcs3

[vs49688]

Huh, TIL cmakeBool exists.

Assuming ofborg passes, lgtm.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/3032/3576

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-already-reviewed/2617/1501

[SuperSandro2000]

@ofborg eval