If you encounter an error concerning Plugins colliding with each other, particularly using ARToolkit and its libARWrapper file, this is because there are several files in your Plugins folder with the same name that are getting linked to the build. Keep the version in Plugins/iOS, but in the other folders, namely x86 and x86_64, select the offending file.

In Inspector, ensure that the iOS platform is not checked, as shown in the following screenshot: