Check for AVX512 at runtime to avoid invalid opcode trap (#8166)

automerge

core/build.rs

@@ -0,0 +1,8 @@
+fn main() {
+    // Until https://github.com/rust-lang/rust/issues/44839 is resolved
+    // `#[target_feature(enable = "avx512f")]` is not available.
+    // Use an env flag instead:
+    if is_x86_feature_detected!("avx512f") {
+        println!("cargo:rustc-env=TARGET_FEATURE_AVX512F=1");
+    }
+}