[Describe your changes and what you've already done to test it.]

In igl::copyleft::cgal::order_facets_around_edges, we need to determine the direction of each undirected edge in order to sort the adjacent facets. This direction is determined by the first directed edge in uE2E[i] list (as shown in this line). However, in the unit test, we are using the direction of uE[i] as the reference direction. This inconsistency causes the unit test in MultipleDuplicatedFaces test case to fail on linux (uE[i] could different on linux and mac, but both are valid since they represent unsigned edge).

Check all that apply (change to [x])

• All changes meet libigl style-guidelines.
• Adds new .cpp file.
• Adds corresponding unit test.
• Adds corresponding python binding.
• This is a minor change.