libidn2: fix darwin build

cc #22595

pkgs/development/libraries/libidn2/default.nix

@@ -1,4 +1,6 @@
-{ fetchurl, stdenv, libiconv, libunistring }:
+{ fetchurl, stdenv, libiconv, libunistring, help2man }:
+
+with stdenv.lib;
 
 stdenv.mkDerivation rec {
   name = "libidn2-0.16";
@@ -10,8 +12,10 @@ stdenv.mkDerivation rec {
 
   outputs = [ "bin" "dev" "out" "info" "devdoc" ];
 
+  patches = optional stdenv.isDarwin ./fix-error-darwin.patch;
+
   buildInputs = [ libunistring ]
-    ++ stdenv.lib.optional stdenv.isDarwin libiconv;
+    ++ optionals stdenv.isDarwin [ libiconv help2man ];
 
   meta = {
     homepage = "https://www.gnu.org/software/libidn/#libidn2";

pkgs/development/libraries/libidn2/fix-error-darwin.patch

@@ -0,0 +1,31 @@
+diff --git a/src/idn2.c b/src/idn2.c
+index 6abbc72..804f0f2 100644
+--- a/src/idn2.c
++++ b/src/idn2.c
+@@ -31,7 +31,6 @@
+ #include <unistr.h>
+ 
+ /* Gnulib headers. */
+-#include "error.h"
+ #include "gettext.h"
+ #define _(String) dgettext (PACKAGE, String)
+ #include "progname.h"
+@@ -161,9 +160,7 @@ process_input (char *readbuf, int flags)
+       free (output);
+     }
+   else
+-    error (EXIT_FAILURE, 0, "%s: %s",
+-	   args_info.register_given ? "register" : "lookup",
+-	   idn2_strerror (rc));
++    perror (idn2_strerror (rc));
+ }
+ 
+ int
+@@ -222,7 +219,7 @@ main (int argc, char *argv[])
+     }
+ 
+   if (ferror (stdin))
+-    error (EXIT_FAILURE, errno, "%s", _("input error"));
++    perror (_("input error"));
+ 
+   cmdline_parser_free (&args_info);