In XCode 6.4 prior to the XCode 7 Beta update, I was able to build my iPhone 5 project. I cannot build it in either and my simulators (iPhone and AppleWatch) can never launch automatically if anything ever builds, I have to open the developer tool manually.
While I know that the older simulators are not available for XCode 7 Beta (and I reverted back to using XCode 6.4), the simulators also do not work as they were working before.