ArgumentException: weird Error

I have a library form a third party in my plugins folder I use with a custom editor tool I made. When I run the scene in the editor the game works fine, also the tool works.

The wield thing is if I try and build a scene it throws a "ArgumentException: The Assembly System.Drawing is reference by ...... But the dll is not allowed to be included or could not be found ....."

What quizzes me most it only on build it throws the error.

The actual build doesn't use the code at all, as its only used as for an editor tool, so a guess I can delete it but there must be a better way.