[iOS] XCode always fails to build for iOS8 with any project

Steps to reproduce:
1. Create a New project
2. Build for iOS
3. Build XCode project for iOS device

Result:XCode fails to build. UnityGfxDeviceWorker (9): signal SIGABRT. XCode Error: ProductName was compiled with optimization - stepping may behave oddly; variables may not be available.

Reproduced with: iOS 8 with 5.6.0b3 and newer.
Not reproduced with: iOS 9, iOS10: 5.6.0b8, 5.5.1p4, 5.4.3p3. iOS8: 5.5.1p4, 5.4.3p3.