Add Apple visionOS support

[QuentinPerez]

Motivation

Add the support of Apple VisionOS 121419

Solution

Add target_os = "visionos"

[Thomasdezeeuw]

Can you add VisionOS to our CI and local testing in:

• mio/Makefile

  Line 2 in 15050b9

  TARGETS ?= aarch64-apple-darwin aarch64-apple-ios aarch64-linux-android arm-linux-androideabi i686-unknown-linux-gnu wasm32-wasi x86_64-apple-darwin x86_64-apple-ios x86_64-pc-windows-gnu x86_64-pc-windows-msvc x86_64-unknown-freebsd x86_64-unknown-illumos x86_64-unknown-linux-gnu x86_64-unknown-linux-musl x86_64-unknown-netbsd x86_64-unknown-redox

• mio/.github/workflows/ci.yml

  Line 145 in 15050b9

  target: ["aarch64-apple-ios", "aarch64-apple-tvos", "aarch64-unknown-openbsd", "arm64_32-apple-watchos", "armv7-sony-vita-newlibeabihf", "sparcv9-sun-solaris", "x86_64-pc-solaris", "x86_64-unknown-dragonfly", "x86_64-unknown-openbsd"]

(same for the socket2 pr, but I'll add a comment there as well)

[Thomasdezeeuw]

libc seems to not build (correctly) for visionOS, see CI.

[QuentinPerez]

see rust-lang/libc#3568 (comment)

[QuentinPerez]

@Thomasdezeeuw same question; do you mind if I use target_vendor = "apple" ? Instead of changing this every time Apple releases a new device

[simlay]

libc seems to not build (correctly) for visionOS, see CI.

It should now be fix with rust-lang/rust#124560. Though, I think CI may still fail because the default Xcode version for the macOS-latest runner is currently Xcode 15.0.1 but visionOS was added with Xcode 15.2 which means that xcrun --show-sdk-path --sdk xros will fail when called from rustc. One could fix this in CI with something like sudo xcode-select -s /Applications/Xcode_15.2.app but that's a bit too specific and brittle for my taste.

[Thomasdezeeuw]

@QuentinPerez can you rebase this after #1787 is merged to give this another try in the cI?

[Thomasdezeeuw]

I've updated this in #1795 to prepare for the changes coming in #1749.