libc 0.2.186 no nto80 branch

[justinlooney]

libc 0.2.186 defines TCP_KEEPALIVE / TCP_KEEPIDLE for target_env = "nto70" / "nto71" (QNX 7.0/7.1) but has no nto80 branch for QNX 8.0

[Darksonn]

What does libc have to say about this?

[Thomasdezeeuw]

@skarlsson you changed this in #654, but it doesn't seem to build. Could you take a look at this? Otherwise we'll have to revert it.

[Thomasdezeeuw]

The only documentation I can find it the following:

• For 7.1: https://www.qnx.com/developers/docs/7.1/com.qnx.doc.neutrino.lib_ref/topic/t/tcp_proto.html, mentions TCP_KEEPALIVE.
• For 8.0: https://www.qnx.com/developers/docs/8.0/com.qnx.doc.neutrino.lib_ref/topic/lib-t.html, it refers to the FreeBSD docs, which uses TCP_KEEPIDLE.

Based on that I think the change is correct, but libc is missing the constant.

For 7.0/7.1 TCP_KEEPALIVE is defined here: https://github.com/rust-lang/libc/blob/2364caf83be0f55ead8bd34dfb82cce66a17c387/src/unix/nto/mod.rs#L919. The solution might be as straightforward as adding the TCP_KEEPIDLE constant to the else branch there.