I also had this same error, and it also indicated having to rebuild many SOs as well as the UE4Editor.
I applied the solution from sam.new but it wasn’t enough. I noticed that UBT is invoked by the editor on start up with:
/path/to/UE4/Engine/Binaries/DotNET/UnrealBuildTool.exe Development Linux -Project="/path/to/project/project.uproject" -TargetType=Editor -Progress -NoEngineChanges -NoHotReloadFromIDE
So, not having anything to lose, I removed the last two command line options as they looked like candidates contributing to the error message and re-invoked it with just:
/path/to/UE4/Engine/Binaries/DotNET/UnrealBuildTool.exe Development Linux -Project="/path/to/project/project.uproject" -TargetType=Editor -Progress
which solved the problem … and allowed me fix the errors causing the failure in the first palce