If that happens on a Mac, what you'll have to do is compile your mod into a dll file by yourself, then in build.txt set noCompile to true and include your dll file in the folder instead of your code. (That's actually the reason I added support for building dll files into mods.)Never mind this won't work because you need to set the permission to run this file and i don't know how to automate that.
PS. I don't think Mac version can build mods. Log says its looking for mono files that even though I have mono installed. Cant build example mod or very simple 1 item mods i made to test it.