This is behavior governed by Perforce. If you are using, for example, a file called .p4ignore in your root, you should add a second .p4ignore file in Unreal4_Base/Engine/Source/Developer with the following contents:
!DerivedDataCache
P4Ignore is cumulative by folder, so this should impact the Developer directory and its subdirectories only.
See more in Perforce’s community support pages.