Disable the use of NEON intrinsics on Miri

Although this happens to work at the moment, there is no guarantee that
this will continue to be the case in the future.

src/raw/mod.rs

@@ -20,15 +20,17 @@ cfg_if! {
     if #[cfg(all(
         target_feature = "sse2",
         any(target_arch = "x86", target_arch = "x86_64"),
-        not(miri)
+        not(miri),
     ))] {
         mod sse2;
         use sse2 as imp;
     } else if #[cfg(all(
         target_arch = "aarch64",
         target_feature = "neon",
         // NEON intrinsics are currently broken on big-endian targets.
+        // See https://github.com/rust-lang/stdarch/issues/1484.
         target_endian = "little",
+        not(miri),
     ))] {
         mod neon;
         use neon as imp;