can't open source EditorUtilityLibrary.h

I’m guessing you’re missing a module in your project. Wiki shows that this class is in the Blutility module. Add it and try building again.

YourProject.build.cs:

using UnrealBuildTool;

public class YourProject : ModuleRules {
	public YourProject(ReadOnlyTargetRules Target) : base(Target) {
		PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;

        // Add public modules here
        PublicDependencyModuleNames.AddRange(new string[] {
            "Core", "CoreUObject", "Engine"
        });

	}
}