How can use IncrediBuild to compile UE4

Probably the latest version is your best bet – but 7.3+ has worked for us.
Do a search for the file BuildConfiguration.xml (there seem to be a few but the one that works for me is in AppData/Roaming/Unreal Engine/UnrealBuildTool). In there set the tag to true. The next build from visual studio should pick it up.
HTH!