Fix errno on DragonFly

[mneumann]

__dfly_error has long been removed from the Rust souce.

[lambda-fairy]

I'm wary of adding another dependency, especially one that has C code.

Is there a way to query the errno directly? I would be happy with what is done in std.

[mneumann]

@lfairy No, it's not possible at the moment with stable rust without a C extension, as thread_local is feature gated (rust-lang/rust#29594). The nix crate has imported my C code into their repository; they didn't like this crate as dependency, but I don't like to repeat that code in multiple crates. If you like you can copy that C code directly... but again, there is atm no other solution.

It works in stdlib only because stdlib is special-cased and allowed to use these features.

[lambda-fairy]

That's reasonable. I'll merge it as-is then.

Thanks!

[mneumann]

@lfairy Thanks!