I have compile error on Xcode 9, and error is Upload: Unable to upload symbol file (reason unknown).
Project compiles successfully on some computer, but
I have found how to avoid this issue. Clean project, delete all derived data and close Xcode. And then, please run below command on terminal.
$ rm $HOME/Library/Preferences/com.google.Symbol*
And open your project on Xcode and build again. Sometimes got same issue, but try above steps one or two times again. This will works for you most of time.