Files like these are and not official releases from Epic Games. It is standard practice to: Scan the .rar file for malware using tools like VirusTotal .
The specific version of Unreal Engine 4 files required to run that build. Fortnite 3.5 reupload by blk.rar
Based on how these "reuploads" are structured by community members like , the archive usually includes: Files like these are and not official releases