How to place packages in a different directory?

I’m sorry if this is common knowledge, but I have searched around without finding an answer.

If I have a custom package, say “common.Utility”, I have to place this in a subdirectory of my project to be able to import it. This is inconvenient if you have a library of common classes that you use in many different projects.

I want to make a directory structure that looks something like this:


and “import common.utillity” from all the projects.

The only solution i have found is to copy the “common” directory under each project, which is horrible.

So, what am I missing?