I use 2 Macs with the same project coming from a git repository.
On the first one, no problem: everything compiles and run smoothly.
On the second new one with a fresh install of MacOS Sierra, I have a issues as soon as I am starting opening the project with Xcode. Sometimes it stops responding instantly (I have to force exit), sometimes it doesn't compile when it should...
What may be the causes of these problems?
Are you opening your project from your Document or your Desktop folder or some subfolders?
If yes, then go to your OS settings, iCloud / iCloud Drive options. Make sure that those folders are NOT checked, or just move your project folder outside of those Document / Desktop folders.
iCloud synchronization of Xcode folders are not working properly yet.