I just downloaded the GM release of Xcode 6 and it won\'t compile with this error:
Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault
I think the real problem is there are too many errors, so the compile tell you only a confused error code.
But you can always open the every source code file, in there you can find the detail error information and correct advice.
Good luck!