create examples/output/ again

[turbomam]

targets that put stuff in examples/output/ may need to create the dir unless we change the cleanup mechanism

the absence of this dir creation step didn't seem to effect the GH Actions but it was leading to make squeaky-clean all test errors on my workstation

[pkalita-lbl]

I think the reason you hit this locally but it doesn't affect any GitHub Actions workflows is that they all use clean and not squeaky-clean. Which begs the question why two? I mean, I can see that they do different things. But why? Regardless, that's a question for another day and this seems fine for now.

[turbomam]

I started adding squeaky-clean targets to my LinkML Makefiles when I was green and didn't want to stray too far from the established clean actions. I agree, its confusing and should be unified or documented better.