问题
After upgrading to Xcode 9.0, existing application getting an error: 
"dyld: dyld_sim not compatible mach-o"
Any comments?
回答1:
In the build setting you need to replace architectures to Standard like as screen shot ... works for me. 
回答2:
Delete the 32bit architecture and use default architecture in build settings
回答3:
This occurred because ios 11 compatible for 64 bites, to solve this issue follow this steps:
1-app target>>Building Settings >>valid Architectures must be in this order armv7 armv7s arm64 2-target>>Building Settings >>Build Architecture Only >> Debug-->YES and release--> NO. 3-.plist :make sure that :Required device Capabilities contain armv7 . 4-if you used third party libraries make sure that this libs compatible with 64 bits.
来源:https://stackoverflow.com/questions/46396330/after-upgrading-to-xcode-9-0-existing-application-getting-an-error-dyld-dyld