Nightly feature stdsimd fails due to removal of the unstable stdsimd feature

[jayvdb]

The commit removing stdsimd is rust-lang/rust@ea37e80

Relevant tracking issues? rust-lang/rust#27731 and rust-lang/rust#48556

> rustup run nightly cargo test --features stdsimd
   Compiling size-of v0.1.5 (/home/jayvdb/rust/size-of)
error[E0658]: use of unstable library feature 'stdarch_x86_avx512'
  --> src/arch/x86_64.rs:23:22
   |
23 |     use super::x86::{__m128bh, __m256bh, __m512, __m512bh, __m512d, __m512i};
   |                      ^^^^^^^^
   |
   = note: see issue #111137 <https://github.com/rust-lang/rust/issues/111137> for more information
   = help: add `#![feature(stdarch_x86_avx512)]` to the crate attributes to enable
   = note: this compiler was built on 2024-02-10; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature 'stdarch_x86_avx512'
  --> src/arch/x86_64.rs:23:32
   |
23 |     use super::x86::{__m128bh, __m256bh, __m512, __m512bh, __m512d, __m512i};
   |                                ^^^^^^^^
   |
   = note: see issue #111137 <https://github.com/rust-lang/rust/issues/111137> for more information
   = help: add `#![feature(stdarch_x86_avx512)]` to the crate attributes to enable
   = note: this compiler was built on 2024-02-10; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature 'stdarch_x86_avx512'
  --> src/arch/x86_64.rs:23:50
   |
23 |     use super::x86::{__m128bh, __m256bh, __m512, __m512bh, __m512d, __m512i};
   |                                                  ^^^^^^^^
   |
   = note: see issue #111137 <https://github.com/rust-lang/rust/issues/111137> for more information
   = help: add `#![feature(stdarch_x86_avx512)]` to the crate attributes to enable
   = note: this compiler was built on 2024-02-10; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature 'stdarch_x86_avx512'
  --> src/macros.rs:6:59
   |
6  |               impl $(<$($generic),*>)? $crate::SizeOf for $($ident)::+ $(<$($generic),*>)? {
   |                                                             ^
   |
  ::: src/arch/x86_64.rs:25:5
   |
25 | /     impl_total_size_childless! {
26 | |         __m128bh,
27 | |         __m256bh,
28 | |         __m512,
...  |
31 | |         __m512i,
32 | |     }
   | |_____- in this macro invocation
   |
   = note: see issue #111137 <https://github.com/rust-lang/rust/issues/111137> for more information
   = help: add `#![feature(stdarch_x86_avx512)]` to the crate attributes to enable
   = note: this compiler was built on 2024-02-10; consider upgrading it if it is out of date
   = note: this error originates in the macro `impl_total_size_childless` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0635]: unknown feature `stdsimd`
 --> src/lib.rs:5:42
  |
5 | #![cfg_attr(feature = "stdsimd", feature(stdsimd))]
  |                                          ^^^^^^^

Some errors have detailed explanations: E0635, E0658.
For more information about an error, try `rustc --explain E0635`.
error: could not compile `size-of` (lib) due to 7 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `size-of` (lib test) due to 7 previous errors