ulex: set platforms

(cherry picked from commit 827a9bbd449ef5075876577ef30703f29f26e597)
Signed-off-by: Domen Kožar <domen@dev.si>

pkgs/development/ocaml-modules/ulex/default.nix

@@ -25,6 +25,7 @@ stdenv.mkDerivation {
     homepage = http://www.cduce.org/download.html;
     description = "ulex is a lexer generator for Unicode and OCaml";
     license = stdenv.lib.licenses.mit;
+    platforms = stdenv.lib.platforms.linux;
     maintainers = [ stdenv.lib.maintainers.roconnor ];
   };
 }