`ofborg-eval-check-meta` does not check `meta.hydraPlatforms` properly

[roberth]

In NixOS/nixpkgs#140585 I accidentally wrapped the platforms in an extra list. Apparently something like

hydraPlatforms = [ [ "x86_64-linux" ] ];

is not caught by ofborg. Nixpkgs does have a line that seems like it should catch it, but clearly the effect of that line is not reaching ofborg. See

https://github.com/NixOS/nixpkgs/blob/f3d4f19fdf4b588b153433cb5d4030cbb09acbe6/pkgs/stdenv/generic/check-meta.nix#L216

[ncfavier]

Fixed by NixOS/nixpkgs#204840, probably?

[ncfavier]

Apparently not. Ofborg failed to catch a double-wrapped platforms in https://github.com/NixOS/nixpkgs/pull/239665/files#r1241160820.

[ncfavier]

Looks like ofborg uses pkgs/top-level/release.nix, which only evaluates packages for the supported platforms... check-meta should happen before that.