Wouldn't have to be open source work, just work you could show.
It's tough to hear, but the goal of a new employer is not to give us what we deserve for working hard and being skilled.
The employer's goal is to maximize their chances of hiring someone good.
If a hiring manager has two people that seem about the same but they can see the code one of those people wrote, it's a no-brainer to go with the one who has a portfolio.
Agree with you that some lame open source patch doesn't matter. But if someone's done significant work in public, or even has non-open-source code they're able to share, ignoring that would be an insane choice for the hiring manager to make.
Yet, mysteriously, civil engineers, material scientists and statisticians somehow keep being hired and the work keeps getting done. Baffling, I know.
I bet you'd hire a programmer without a degree who can do the work before you'd hire a civil engineer who learned how to build stuff off the Internet. :)
but since people can show it in the programming world, you are at a disadvantage if you don't.
if a civil engineer had some way to show what they could do, I'm sure it'd give them an advantage.