Xcode 9 Bug: Cannot find cdtool

Question

After installing Xcode 9 beta, Xcode 8 gives me an error when compiling a project:

Cannot find cdtool at \'/Applications/Xcode.app/Contents/Developer/

Answer 1

Didn't work for me because I also have a Watch app and got the error on the Watch SDK.

I ended up deleting both Xcode 8 and 9 Beta, deleting /Library/Developer and ~/Library/Developer. Then reinstalled Xcode 8 and it worked.