Fix UnixSockets classpath detection logic

[mpilquist]

Fixes #2623

[armanbilge]

Do we care enough to add any sort of regression tests?

[mpilquist]

I don't know how we could do that. Good news is that http4s build will validate this though.

[armanbilge]

Can't we do CI for fs2 on older JDKs? It's only UnixSockets that needs JDK 16 right, and this is specifically what we'd want to test?

[vasilmkd]

It complicates the build with two JDKs, one for building, one for running.

[armanbilge]

Yeah, now that its being tested downstream probably more trouble than it's worth.

[mpilquist]

Yeah, not sure what that build would even look like. If we tried just running the same test suite on a different JDK, then SBT will recompile everything. We'd have to somehow publish artifacts somewhere and then run a completely different SBT project using those artifacts.

[armanbilge]

We'd have to somehow publish artifacts somewhere and then run a completely different SBT project using those artifacts.

Aren't the artifacts already pushed into GHA cache?

[mpilquist]

Yes but SBT will notice the JDK changed and invalidate them / rebuild them.