Oh, in Applications > Utilities - you will find the Terminal app.

With the Terminal app opened, you can drag your Cycles standalone app there (to get it's location), then add a space and then drag your xml file to the Terminal window and hit enter.
This will render your xml in Cycles standalone on OSX.

Did this very fast test, to see if it worked. Pretty sweet render of glass in 30 seconds on a laptop! Like the Cycles renderer! :-D