It would need to be a fairly high profile open source project, one that would attract the attention of recruiters. Of course, you'd be compared against the other high profile contributors to it, but what better way to show you can do it?

There are other ways to raise one's profile. One could join the C++ Standard committee and actively participate in it. The top C++ companies will notice you. Or the standards committee of your favorite language.

One can submit papers to relevant conferences. Companies often attend conferences for the specific purpose of recruiting.

Even better, you can do the above without needing to relocate, and with minimal investment of funds.

Interesting thoughts, thanks for sharing