How can I delete derived data in Xcode 8?

(Working in Xcode 11 and 12)

You can go to File > Workspace Settings if you are in a workspace environment or File > Project Settings for a regular project environment.

Then click over the little grey arrow under Derived data section and select your project folder to delete it.

The simplest and fastest way is the following (if you have not changed the defaults folder for DerivedData).

Open terminal and past the following:

rm -rf ~/Library/Developer/Xcode/DerivedData