🚑️ zb: Fix sendmsg for iOS and other apple OS

[dtolnay]

Since #1660 zbus is unable to build for iOS.

$ cargo check --target=aarch64-apple-ios
error[E0599]: no associated item named `NOSIGNAL` found for struct `SendFlags` in the current scope
   --> zbus/src/connection/socket/unix.rs:330:28
    |
330 |     let flags = SendFlags::NOSIGNAL;
    |                            ^^^^^^^^ associated item not found in `SendFlags`

[codspeed-hq]

Merging this PR will not alter performance

✅ 22 untouched benchmarks

---

_{Comparing dtolnay-contrib:ios (40d8995) with main (aa34b2d)}

[zeenix]

@dtolnay Thanks! I will take care of modifying the commit message for you, don't worry about it.

While I have your attention: serde-rs/serde#2045 has been a real PITA for me in the zlink project. @RaitoBezarius has graciously volunteered to try and provide a PR for this so I'd really appreciate it if you could review that (and merge if it's good) when they've provided it. 🙏 Of course, me merging this good PR is not at all conditioned on that. 😉

[zeenix]

oh and btw, I'm very surprised to hear that people use zbus on iOS. 😮

[zeenix]

@dtolnay Thanks! I will take care of modifying the commit message for you, don't worry about it.

I guess you didn't opt for the "Allow maintainers to apply changes to the PR":

❯ git push dtolnay ios -f
ERROR: Permission to dtolnay-contrib/zbus.git denied to zeenix.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

Please either allow me to do that or just modify the commit and add the 🚑️ to the commit title.