In Xcode 8 you can't. They briefly had it as a feature but it has never worked properly and is not supported.
EDIT: It was also using Wi-Fi, not Bluetooth.
Correct. I've hacked at it a bit in an attempt to re-enable the functionality but I haven't been successful yet. After reversing some old XCodes and iOS binaries I found a MobileDevice.framework call that is related to WiFi debugging but even after poking the iDevice with it, XCode doesn't show it in it's device list.
extern int AMDeviceSetWirelessBuddyFlags(struct am_device *device, uint8_t flags);
AMDeviceSetWirelessBuddyFlags(device, 1|2);