After installing Xcode 9 beta, Xcode 8 gives me an error when compiling a project:
Cannot find cdtool at \'/Applications/Xcode.app/Contents/Developer/
You can also remove the 10.3 folder from /Library/Developer/CoreSimulator/Profiles/Runtimes
/Library/Developer/CoreSimulator/Profiles/Runtimes
Restart Xcode in order to take effect (may not be needed).