In Xcode 8, all the derived data is automatically cleaned. If you want to do it by hand, go to Locations
tab from the Preferences
, locate project's derived data folder, and delete files related to the project.
In macOS 10.12 and later, Xcode cleans up stale derived data, precompiled headers, and module caches. (23282174)
Credits to @charmingToad
But from what I observed, the same behaviour is typical when using Xcode 8 on OS X 10.11.5/6