treat errno(6) (NXIO) as expected error in openatZ

[bfreis]

This PR adds explicitly handling of NXIO (errono(6)) to std.posix.openatZ to avoid verbose output when this error occurs.

related to: #18240

[bfreis]

Not sure if error.NoDevice is the best choice here, but I couldn't find anything on OpenError that was more suitable. Would it be better to add something new to OpenError instead?

[squeek502]

Coincidentally, this exact topic came up in a separate recent PR here: #21938

No conclusion about the name of the error has been made yet, so feel free to make suggestions if you have them.

[andrewrk]

Thanks!

[alexrp]

I'm confused about this PR's relation to #18240; that issue is about write, while this is about openat?

[bfreis]

I'm confused about this PR's relation to #18240; that issue is about write, while this is about openat?

You're right, it's a different operation - the relation I saw was that the "theme" and the type of fix is the same: Zig didn't account for errno 6 being a possible, expected error, and treats it as unexpected by being very verbose about it.

A fix to that other issue would likely be very similar, but on write instead of openat.

[alexrp]

Ok, I'll reopen that issue then.