Why does iOS try to compile all DLL's?

Hello,

I have a project I build for PC/Android/iOS. On PC/Android it behaves as expected, in that it only compiles the stuff that is referenced/used by my scripts.

On iOS however it seem to try to compile every single DLL in my Assets/ even though they aren't used. And that makes it very hard to build for PC/Android and iOS in the same project, since the compilation of PC/Android dll's will fail. For example it will try to compile a Android-specific dll I built that I have placed in Assets/plugins/Android and is only used for UNITY_ANDROID

Why does it do this? How can you fix it?