libidn2: fix build on darwin

The documentation requirements changed after the version upgrade in
https://github.com/NixOS/nixpkgs/pull/123059.

pkgs/development/libraries/libidn2/default.nix

···
-{ fetchurl, lib, stdenv, libiconv, libunistring, help2man, buildPackages }:
+{ fetchurl, lib, stdenv, libiconv, libunistring, help2man, texinfo, buildPackages }:
 
 # Note: this package is used for bootstrapping fetchurl, and thus
 # cannot use fetchpatch! All mutable patches (generated by GitHub or
···
 
   patches = optional stdenv.isDarwin ./fix-error-darwin.patch;
 
-  nativeBuildInputs = optional stdenv.isDarwin help2man;
+  # The above patch causes the documentation to be regenerated, so the
+  # documentation tools are required.
+  nativeBuildInputs = optionals stdenv.isDarwin [ help2man texinfo ];
   buildInputs = [ libunistring ] ++ optional stdenv.isDarwin libiconv;
   depsBuildBuild = [ buildPackages.stdenv.cc ];