discord: add libglvnd and fix electron flags

[fufexan]

Description of changes

Fixes Discord Canary not launching in Wayland mode when NIXOS_OZONE_WL=1 is set (broken in #192659), and errors such as

[2946:1122/160729.555518:ERROR:egl_util.cc(74)] Failed to load GLES library: libGLESv2.so.2: libGLESv2.so.2: cannot open shared object file: No such file or directory

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.11 Release Notes (or backporting 22.05 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
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[SuperSamus]

Is it related to the issue #159267?

[fufexan]

Not entirely sure, I didn't have a black screen before.

[Artturin]

i can't reproduce the issue on my amd gpu but there's some vendored libraries in opt/DiscordCanary

$ pwd
/nix/store/k1kcpdbqk7h9ssg2pqsvzc432g1wy2qf-discord-canary-0.0.143/opt/DiscordCanary
$ ls *.so
 libEGL.so   libffmpeg.so   libGLESv2.so   libvk_swiftshader.so

[Infinidoge]

Unfortunately I do not currently have a Wayland setup, so I cannot (and have not) personally tested this to see if this actually fixes that issue. However, the code changes look good to me, and it runs properly under X11. I also didn't see any cannot open shared object file errors.

[fufexan]

i can't reproduce the issue on my amd gpu but there's some vendored libraries in opt/DiscordCanary

$ pwd
/nix/store/k1kcpdbqk7h9ssg2pqsvzc432g1wy2qf-discord-canary-0.0.143/opt/DiscordCanary
$ ls *.so
 libEGL.so   libffmpeg.so   libGLESv2.so   libvk_swiftshader.so

I've tested again and it seems that it only fails to find those libs when building with OpenASAR.

However the Wayland --ozone-platform is wrong either way, and works using this PR.

[fufexan]

@Artturin does my comment above address your question? Should we look for alternatives?