Xcode 6 works on pyshical iPhone but not simulator - Cocoa Pods file errors

I just installed XCode 6 and something strange is happening.

I can run my app on a physical iOS7 phone, but not in a simulator, so this means the app is working fine.

When I build in simulator I get this error:

file '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/usr/include/sysexits.h' was modified after pre-compiling the header '/ Users / xxxxxx / Library /Developer/Xcode/DerivedData/xxxxx-bssuvokuewryahcpprljeeteqzui/Build/Intermediates/PrecompiledHeaders/Pods-xxxxx-Mantle-prefix-eoukyqdtliihgbfojcbqdtliihgbfojcbqetlttnwe/Pods was built-xxpxxx '

I tried:

• Cleaning up the project
• Deleting a folder with derived data
• Remove cocoa pods in the following project: How to remove CocoaPods from a project?

I think it just has to do with the simulator, but I don't know what I can do. Any ideas?