Has anyone run into this issue? I was experimenting with porting an existing obj-c app to Swift, and after quite a few successful builds the project will no longer build and immediately gives the error: Unable to run command 'CompileSwift normal' - this target might include its own product. Along with many other 'target might include it's own product errors'.
What I've Tried:
I had the same issue. I couldn't work out exactly what was causing it, but realised the same code would build find on a different Xcode 6 install on a different machine.
I solved it by deleting my cached builds, etc, in
~/Library/Developer/Xcode, while Xcode is not running. "Clean" alone from within Xcode didn't do it.
You should find that when you re-launch Xcode your app will build fine.