Replace sa_sigaction with sa_union.__su_sigaction for AIX.

tests/ui/runtime/on-broken-pipe/auxiliary/assert-sigpipe-disposition.rs

@@ -25,7 +25,14 @@ fn start(argc: isize, argv: *const *const u8) -> isize {
     let actual = unsafe {
         let mut actual: libc::sigaction = std::mem::zeroed();
         libc::sigaction(libc::SIGPIPE, std::ptr::null(), &mut actual);
-        actual.sa_sigaction
+        #[cfg(not(target_os = "aix"))]
+        {
+            actual.sa_sigaction
+        }
+        #[cfg(target_os = "aix")]
+        {
+            actual.sa_union.__su_sigaction as libc::sighandler_t
+        }
     };
 
     assert_eq!(actual, expected, "actual and expected SIGPIPE disposition in child differs");

tests/ui/runtime/on-broken-pipe/auxiliary/sigpipe-utils.rs

@@ -20,7 +20,14 @@ pub fn assert_sigpipe_handler(expected_handler: SignalHandler) {
         let actual = unsafe {
             let mut actual: libc::sigaction = std::mem::zeroed();
             libc::sigaction(libc::SIGPIPE, std::ptr::null(), &mut actual);
-            actual.sa_sigaction
+            #[cfg(not(target_os = "aix"))]
+            {
+                actual.sa_sigaction
+            }
+            #[cfg(target_os = "aix")]
+            {
+                actual.sa_union.__su_sigaction as libc::sighandler_t
+            }
         };
 
         let expected = match expected_handler {

tests/ui/runtime/signal-alternate-stack-cleanup.rs

@@ -29,7 +29,14 @@ fn main() {
         // Install signal handler that runs on alternate signal stack.
         let mut action: sigaction = std::mem::zeroed();
         action.sa_flags = (SA_ONSTACK | SA_SIGINFO) as _;
-        action.sa_sigaction = signal_handler as sighandler_t;
+        #[cfg(not(target_os = "aix"))]
+        {
+            action.sa_sigaction = signal_handler as sighandler_t;
+        }
+        #[cfg(target_os = "aix")]
+        {
+            action.sa_union.__su_sigaction = signal_handler as sighandler_t;
+        }
         sigaction(SIGWINCH, &action, std::ptr::null_mut());
 
         // Send SIGWINCH on exit.