src: set SA_SIGINFO flag when using sa_sigaction

For `sigaction()` the `SA_SIGINFO` flag should be set when setting
the handler via the `sa_sigaction` member of the `sigaction` struct.

src/node.cc

@@ -543,7 +543,7 @@ void RegisterSignalHandler(int signal,
   struct sigaction sa;
   memset(&sa, 0, sizeof(sa));
   sa.sa_sigaction = handler;
-  sa.sa_flags = reset_handler ? SA_RESETHAND : 0;
+  sa.sa_flags = reset_handler ? SA_RESETHAND | SA_SIGINFO : SA_SIGINFO;
   sigfillset(&sa.sa_mask);
   CHECK_EQ(sigaction(signal, &sa, nullptr), 0);
 }
@@ -638,6 +638,7 @@ inline void PlatformInit() {
     struct sigaction sa;
     memset(&sa, 0, sizeof(sa));
     sa.sa_sigaction = TrapWebAssemblyOrContinue;
+    sa.sa_flags = SA_SIGINFO;
     CHECK_EQ(sigaction(SIGSEGV, &sa, nullptr), 0);
   }
   V8::EnableWebAssemblyTrapHandler(false);

test/addons/register-signal-handler/binding.cc

@@ -13,6 +13,7 @@ using v8::Value;
 void Handler(int signo, siginfo_t* siginfo, void* ucontext) {
   char signo_char = signo;
   int written;
+  assert(signo == siginfo->si_signo);
   do {
     written = write(1, &signo_char, 1);  // write() is signal-safe.
   } while (written == -1 && errno == EINTR);