Exclude file from Build

Is it possible to dynamically include or exclude a file when making a build? I have a specific plugin DLL that I want to exclude for certain builds, but include for others. I'm not ready to convert to Unity 5, so I'm hoping there's a supported way in 4.6.

 

Preprocessor directives should do the trick:

https://msdn.microsoft.com/en-us/library/4y6tbswk.aspx

 

This allows certain portions of code to be excluded, but I don't believe it will work for excluding a file, such as a DLL in the plugins folder. Please let me know if there's a way to use directives for file exclusion.

 

I think you can do that by putting the DLL in the Plugins folder and either fiddling with the Inspector if you're on version 5.0 or placing the DLL in a specially named subfolder if you're using earlier version. Documentation has the gritty details.