Unable to determine the compiler to use - the abstract compiler spec is missing from this Xcode installation

Hi I have an iMac with OS X Yosemite version 10.10.3 and I have installed the latest Xcode 6.3 beta 2 with Swift 1.2 and when I try to run the application I get: Check dependencies Cannot determine the compiler to use - there is no abstract compiler specification in this Xcode installation.

and every time I open my project with Xcode I get a warning: warning: no rule to handle file '/ Users / Bogdan-iMac / Desktop / My App / My App / My_App.xcdatamodel' type wrappers for x86_64 architecture and i need to open Build Phases in Compile Sources i need to remove My_App.xcdatamodel and add it again to prevent warning

Apple Dev Forums link: https://devforums.apple.com/thread/263126