weechat-matrix-bridge: mark package as broken as Darwin

All of the dependencies of this package are now available on Darwin, but
the package itself still fails to build on that platform.

pkgs/applications/networking/irc/weechat/scripts/weechat-matrix-bridge/default.nix

@@ -42,5 +42,9 @@ stdenv.mkDerivation {
     maintainers = with maintainers; [ ma27 ];
     license = licenses.mit; # see https://github.com/torhve/weechat-matrix-protocol-script/blob/0052e7275ae149dc5241226391c9b1889ecc3c6b/matrix.lua#L53
     platforms = platforms.unix;
+
+    # As of 2019-06-30, all of the dependencies are available on macOS but the
+    # package itself does not build.
+    broken = stdenv.isDarwin;
   };
 }