fix(android/aarch64): use libc::ucontext_t from Android NDK

Author: StackOverflowExcept1on

src/unix/linux_like/android/b32/arm.rs

@@ -31,7 +31,7 @@ s! {
 
     pub struct __c_anonymous_uc_sigmask_with_padding {
         pub uc_sigmask: crate::sigset_t,
-        /* Android has a wrong (smaller) sigset_t on x86. */
+        /* Android has a wrong (smaller) sigset_t on ARM. */
         __padding_rt_sigset: Padding<u32>,
     }
 

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

@@ -63,7 +63,10 @@ s! {
         pub uc_flags: c_ulong,
         pub uc_link: *mut ucontext_t,
         pub uc_stack: crate::stack_t,
-        pub uc_sigmask: crate::sigset_t,
+        pub uc_sigmask__c_anonymous_union: __c_anonymous_uc_sigmask,
+        /* The kernel adds extra padding after uc_sigmask to match
+         * glibc sigset_t on ARM. */
+        __padding: Padding<[c_char; 128 - size_of::<crate::sigset_t>()]>,
         pub uc_mcontext: mcontext_t,
     }
 
@@ -85,6 +88,11 @@ s! {
 }
 
 s_no_extra_traits! {
+    pub union __c_anonymous_uc_sigmask {
+        uc_sigmask: crate::sigset_t,
+        uc_sigmask64: crate::sigset64_t,
+    }
+
     #[repr(align(16))]
     pub struct max_align_t {
         priv_: [f32; 8],