I have got this warning when upgrade my project:
directory not found for option \'-F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.p
I had the same error with Xcode 9.2 and here is my solution:
This is what the screen looked like before deleting
I recently upgraded my project as well and ran into the same thing. This fixed it for me:
https://stackoverflow.com/a/32620919/3279011
Note that you need to edit the properties of the test-project, not your main one (that's what took me a while to process).