gnupg: fix cross compilation

[uninsane]

when npth upgraded 1.6 -> 1.7, the npth-config binary it previously provided was removed, and functionality folded into gpgrt-config. see: https://github.com/gpg/npth/blob/417abd56fd7bf45cd4948414050615cb1ad59134/NEWS#L8

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux (for .#pkgsCross.aarch64-multiplatform.gnupg)
  • 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
  • not all dependents, but successfully built a sway+gtk desktop with this patch.
• 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
• Fits CONTRIBUTING.md.

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[danielbarter]

Tested using
nix-build -E 'with import /path/to/nixpkgs {}; pkgsCross.aarch64-multiplatform.gnupg.override { enableMinimal = true;}'
and everything looks good.

[tpwrules]

Ran into this issue too. gnupg was able to find gpgrt-config in a native scenario because it was on $PATH, being supplied as a buildInput. Specifying it directly in this way allows it to be found in a cross scenario as well.

Tested native x86_64-linux, aarch64-linux, and x86_64-linux -> aarch64-linux.

[Mindavi]

If possible it may also be a good idea to enable strictDeps. But make sure to verify native compilation for that.

[colemickens]

Is anyone running with this PR, and uses an openpgp smartcard or yubikey? I can't tell quite what's going on but gpg --card-status is hanging for me, regardless of if the card is inserted...

EDIT: I don't have any idea what was going on but I have no issues after rebooting into the same generation.

[nixos-discourse]

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

https://discourse.nixos.org/t/why-does-nixos-rebuild-want-me-to-install-a-library/43733/14