call C# dll class in plugins from JavaScript

I am trying to call functions from a class in a C# dll I made, that I have put in my Plugins folder, from a javascript function. This works fine in the editor, but whenever I try to build the scene I get a compiler error saying that the javascript function can't find my C# class.

I have already made sure that my C# class is in the plugins folder to be compiled first, and even tried to use the Script Execution Order tool unity has to make sure this javascript is compiled afterwards but it doesn't seem to make a difference.

Does anyone know what might be the difference between running these scripts together in the editor and trying to make a build of any sort?