dirmngr: supports darwin

pkgs/tools/security/dirmngr/default.nix

@@ -1,4 +1,5 @@
-{ stdenv, fetchurl, libgpgerror, libgcrypt, libassuan, libksba, pth, openldap }:
+{ stdenv, fetchurl, libgpgerror, libgcrypt, libassuan, libksba, pth, openldap
+, libiconv}:
 
 stdenv.mkDerivation rec {
   name = "dirmngr-1.1.1";
@@ -6,9 +7,10 @@ stdenv.mkDerivation rec {
     url = "mirror://gnupg/dirmngr/${name}.tar.bz2";
     sha256 = "1zz6m87ca55nq5f59hzm6qs48d37h93il881y7d0rf2d6660na6j";
   };
-  buildInputs = [ libgpgerror libgcrypt libassuan libksba pth openldap ];
+  buildInputs = [ libgpgerror libgcrypt libassuan libksba
+                  pth openldap libiconv ];
 
   meta = {
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.unix;
   };
 }