"The file "MyApp.app" couldn't be opened because you don't have permission to view it" when running app in Xcode 6 Beta 4

I use Xcode6 GM. I encountered the same problem. What I did was to go to Build Settings -> Build Options. Then I changed the value of the "Compiler for C/C++/Objective-C" to Default Compiler.

Having the problem on DEVICE too (not just simulator)?

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The other solutions only fixed it for me on simulator, not device.

For me this problem occurred (in Xcode 6) when I would try to change the main info.plist properties whilst trying to change my app name.

In info.plist I had changed Executable File name to something other than the default ${EXECUTABLE_NAME}...

I had mistaken this field for the field that changes the name of the app under the icon on the springboard.

In Xcode do the following

Window --> Organiser --> Projects --> The app with the issue --> delete button in Derived Data.

I then cleaned the project and voila

works