Add ugly mastodon build fix

patches/mastodon.patch

@@ -0,0 +1,16 @@
+diff --git a/pkgs/servers/mastodon/default.nix b/pkgs/servers/mastodon/default.nix
+index 8f34d284df2..9d1a25e4e97 100644
+--- a/pkgs/servers/mastodon/default.nix
++++ b/pkgs/servers/mastodon/default.nix
+@@ -31,9 +31,10 @@ stdenv.mkDerivation rec {
+         cp -a "$gem/" "$gem.new"
+         rm "$gem"
+         # needed on macOS, otherwise the mv yields permission denied
+-        chmod +w "$gem.new"
++        chmod -R +w "$gem.new"
+         mv "$gem.new" "$gem"
+       done
++      cp "$out"/lib/ruby/gems/*/gems/blurhash-*/lib/encode.so "$out"/lib/ruby/gems/*/gems/blurhash-*/ext/blurhash/
+     '';
+   };
+