I would suggest asking a family member/friend/school if you can use and download xcode on their Mac. I am sorry I can't give better news about the subject. Testflight requires you to have a apple developer account which is 99 dollars a year. I was on the linux forums when I heard that, apparently the linux/windows community agrees that it can't be done that way. Apple warns against using Xcode in a VM because it does not work.
