add declaration of max_align_t for macOS on aarch64

Author: bsteinb

src/unix/bsd/apple/b64/aarch64/align.rs

@@ -1,3 +1,10 @@
+s_no_extra_traits! {
+    #[allow(missing_debug_implementations)]
+    pub struct max_align_t {
+        priv_: f64
+    }
+}
+
 s! {
     pub struct __darwin_mcontext64 {
         pub __es: __darwin_arm_exception_state64,

src/unix/bsd/apple/b64/mod.rs

@@ -121,13 +121,6 @@ extern "C" {
     ) -> ::c_int;
 }
 
-cfg_if! {
-    if #[cfg(libc_align)] {
-        mod align;
-        pub use self::align::*;
-    }
-}
-
 cfg_if! {
     if #[cfg(target_arch = "x86_64")] {
         mod x86_64;

src/unix/bsd/apple/b64/x86_64/align.rs

@@ -0,0 +1,7 @@
+s_no_extra_traits! {
+    #[allow(missing_debug_implementations)]
+    #[repr(align(16))]
+    pub struct max_align_t {
+        priv_: [f64; 2]
+    }
+}

src/unix/bsd/apple/b64/x86_64.rs renamed to src/unix/bsd/apple/b64/x86_64/mod.rs

@@ -93,3 +93,10 @@ s! {
         pub __xmm_reg: [::c_char; 16],
     }
 }
+
+cfg_if! {
+    if #[cfg(libc_align)] {
+        mod align;
+        pub use self::align::*;
+    }
+}