Motivation for this change

The WiFi regulatory database (CRDA) is a list, by country, of which frequencies are legal for use and how to use them. If it's missing, the kernel will use a global ruleset that might be just the intersection of what's legal in every country.

As many devices (e.g. phone hotspots) automatically apply the correct CRDA rules, it's possible for a hotspot to allocate a frequency band which is not globally legal. This is normally fine, as AP scans can be done passively and the beacons will include a country code for setting up CRDA on the client, but if the CRDA database is missing then the udev event will go unheeded.

In practice this means access points will either become impossible to connect to, or outright invisible. The problem is especially insidious because it's likely to occur during travel, when you may not have any other options for connecting to a network.

This commit enables CRDA if either wpa_supplicant or networkmanager is enabled, adding 264KiB to the closure size in either case.

There should be no documentation needed; it's entirely plug and play.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• 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 nix-review --run "nix-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.