add stdarch_x86_avx512 feature flag for AVX-512-supporting architectures

Author: AquaEBM

crates/core_simd/src/lib.rs

@@ -33,6 +33,10 @@
     any(target_arch = "powerpc", target_arch = "powerpc64"),
     feature(stdarch_powerpc)
 )]
+#![cfg_attr(
+    all(target_arch = "x86_64", target_feature = "avx512f"),
+    feature(stdarch_x86_avx512)
+)]
 #![warn(missing_docs, clippy::missing_inline_in_public_items)] // basically all items, really
 #![deny(unsafe_op_in_unsafe_fn, clippy::undocumented_unsafe_blocks)]
 #![allow(internal_features)]