Fix alignment of uc_ucontext fields on arm64 android (rust-lang#3894)

[ change `core` to `::core` and move ucontext_t to s_no_extra_traits for
  backport - Trevor ]
(backport <rust-lang#3894>)
(cherry picked from commit 707d32c)

Author: CUB3D

src/unix/linux_like/android/b64/aarch64/align.rs

@@ -0,0 +1,31 @@
+s_no_extra_traits! {
+    #[allow(missing_debug_implementations)]
+    #[repr(align(16))]
+    pub struct max_align_t {
+        priv_: [f32; 8]
+    }
+
+    #[allow(missing_debug_implementations)]
+    pub struct ucontext_t {
+        pub uc_flags: ::c_ulong,
+        pub uc_link: *mut ucontext_t,
+        pub uc_stack: ::stack_t,
+        pub uc_sigmask: ::sigset_t,
+        pub __pad: [u8; 1024 / 8 - ::core::mem::size_of::<::sigset_t>()],
+        pub uc_mcontext: mcontext_t,
+    }
+}
+
+s! {
+    #[repr(align(16))]
+    pub struct mcontext_t {
+        pub fault_address: ::c_ulonglong,
+        pub regs: [::c_ulonglong; 31],
+        pub sp: ::c_ulonglong,
+        pub pc: ::c_ulonglong,
+        pub pstate: ::c_ulonglong,
+        // nested arrays to get the right size/length while being able to
+        // auto-derive traits like Debug
+        __reserved: [[u64; 32]; 16],
+    }
+}