The main reason causing this is the file name: file ConvexHull2d.h is located in Engine/Source/Runtime/Core/Public/Math/ConvexHull2D.h and is named “ConvexHull2d.h”
Most Linux distributions has ext filesystem and ext is case sensitive. It means in ext files located in the same directory and named “ConvexHull2D.h” and “ConvexHull2d.h” are considered as different files. The workaround is to rename the file “ConvexHull2d.h” to "ConvexHull2D.h.
P.S. Sorry, didn’t find another way to report this.