Yesterday, I\'ve downloaded beta version of Xcode 11. After that, I\'ve opened my project and tried to run with new Xcode. Unfortunately error has occurred with message:
I ran into this same issue as well.
I didn't get so far as to trying some of the other options provided here, but I was able to get back to building for simulator by simply deleting the /DerivedData directory.
If you're unsure as to where to find it, simply do this: Xcode -> Preferences -> Locations and select the arrow next to the path for Derived Data