Under features = ["nightly_stdsimd"], only enable stdarch_x86_avx512 feature on x86 or x86_64 targets

[zachs18]

... as the feature does not exist on other targets.

$ cargo new mwe
$ cd mwe
$ cargo add bytemuck -F nightly_stdsimd
$ cargo +nightly build --target aarch64-unknown-linux-gnu
   Compiling bytemuck v1.14.2
error[E0635]: unknown feature `stdarch_x86_avx512`
 --> /home/zachary/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bytemuck-1.14.2/src/lib.rs:7:50
  |
7 | #![cfg_attr(feature = "nightly_stdsimd", feature(stdarch_x86_avx512))]
  |                                                  ^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0635`.
error: could not compile `bytemuck` (lib) due to 1 previous error

[Lokathor]

I'm shouting and stamping my foot at the existence of other arches, and also at the same time trying to get people to program for an ARM target. Such is life.

[Lokathor]

Released bytemuck-1.14.3