mesa: 19.3.3 -> 20.0.1

[primeos]

New APIs implemented: Vulkan 1.2
Mesa 20 also prefers iris (new driver) over i965 by default on newer Intel iGPUs (Gen8+).

Motivation for this change

I noticed that the package is a bit outdated.

Note: Alternatively we could switch to 19.3.5 ("This is a bug fix release, and the final 19.3.x release. Users are encouraged to migrate to 20.0.x in order to obtain future fixes.") and e.g. wait for 20.0.2 (but 20.0.1 should be stable).

Things done

• 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.

[primeos]

I didn't notice any issues so far.

I did test a few rebuilds and replaced only the drivers in /run/opengl-driver on my test setup (AMD Radeon HD 6950 - tested Sway, i3, glxinfo, and glxgears).

[vcunat]

Switching to 20.0.1 sounds good in principle.

19.3.5 might be good for our release-20.03. There would probably be a slight disadvantage of not testing that version on our unstable/master first, but for these small updates I expect the risks/fixes ratio will be good enough.

[primeos]

@vcunat do you have a preference? It didn't sound like it (at least not a strong one) but just to be sure.

I didn't consider backporting but agree that using 19.3.5 for 20.03 might be a good idea. However, if we test 19.3.5 on nixos-unstable first there might also be the disadvantage that it won't land in 20.03 until the final release (due to 2x staging), which might also be undesirable (during the beta phase minor bugs would IMO be less problematic than after the final release).

Anyway, you have way more experience with this package so I'd like to leave the decision up to you (might also make sense to ask @NixOS/backports).

[vcunat]

Certainly not a strong one, from what I know at this moment.