Allow YAML on other platforms as well.

pkgs/development/libraries/libyaml/default.nix

@@ -14,7 +14,7 @@ stdenv.mkDerivation {
     homepage = http://pyyaml.org/;
     description = "A YAML 1.1 parser and emitter written in C";
     license = licenses.mit;
-    platforms = platforms.unix;
+    platforms = platforms.all;
     maintainers = with maintainers; [ wkennington ];
   };
 }