FASTBuild for UE 4.21 /Engine/Source/Programs/UnrealBuildTool/Executors/Experimental/FASTBuild.cs Adds support to use FASTBuild distributed compilation by UE4 https://github.com/liamkf/Unreal_FASTBuild/blob/master/LICENSE Licensees Git P4 /UE4/Main/Engine/Source/ThirdParty/Licenses/UnrealFASTBuild_v0-95