@AT Mike: I suspect you reused your SDK, which implies you reused your LLVM module cache. Try cleaning the compiler cache (checkbox "Compiler cache: clean") and let me know if it fixes the problem. Also please note that locating your Xcode project closer to the drive root (here you are at "E:/Unity Projects/Builds/AT_Centrica/iOS/31 test/") is likely to avoid problems with the Windows maximum pathname length limitation of 260 characters. That's why the builder recommends that you put your Xcode projects in C:\iOS (or any other location as close as possible to a drive root).