ucontext usage update on macos 64 bits.

closes rust-lang#2812

Author: devnexen

libc-test/build.rs

@@ -324,6 +324,9 @@ fn test_apple(target: &str) {
             // macOs 12 minimum
             "backtrace_async" => true,
 
+            // deprecated api
+            "getcontext" => true,
+
             _ => false,
         }
     });

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

@@ -15,6 +15,7 @@ s! {
         pub uc_link: *mut ::ucontext_t,
         pub uc_mcsize: usize,
         pub uc_mcontext: mcontext_t,
+        __mcontext_data: __darwin_mcontext64,
     }
 
     pub struct __darwin_mcontext64 {

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

@@ -109,6 +109,9 @@ extern "C" {
         path2: *const ::c_char,
         options: ::c_uint,
     ) -> ::c_int;
+
+    #[allow(deprecated)]
+    pub fn getcontext(context: *mut ::ucontext_t) -> ::c_int;
 }
 
 cfg_if! {