racket: on darwin, use libiconv

Without libiconv, racket doesn't support UTF-16, and this breaks one
of the tests.

Closes #34576

pkgs/development/interpreters/racket/default.nix

@@ -1,6 +1,8 @@
 { stdenv, fetchurl, makeFontsConf, makeWrapper
 , cairo, coreutils, fontconfig, freefont_ttf
-, glib, gmp, gtk2, libedit, libffi, libjpeg
+, glib, gmp, gtk2, libedit, libffi
+, libiconv
+, libjpeg
 , libpng, libtool, mpfr, openssl, pango, poppler
 , readline, sqlite
 , disableDocs ? false
@@ -54,7 +56,7 @@ stdenv.mkDerivation rec {
   ];
 
   buildInputs = [ fontconfig libffi libtool makeWrapper sqlite ]
-    ++ stdenv.lib.optionals stdenv.isDarwin [ CoreFoundation ];
+    ++ stdenv.lib.optionals stdenv.isDarwin [ libiconv CoreFoundation ];
 
   preConfigure = ''
     unset AR
@@ -92,6 +94,6 @@ stdenv.mkDerivation rec {
     homepage = http://racket-lang.org/;
     license = licenses.lgpl3;
     maintainers = with maintainers; [ kkallio henrytill vrthra ];
-    platforms = [ "x86_64-linux" ];
+    platforms = [ "x86_64-darwin" "x86_64-linux" ];
   };
 }