Block other signals while handling a signal.

runtime/bin/process_macos.cc

Index: runtime/bin/process_macos.cc
diff --git a/runtime/bin/process_macos.cc b/runtime/bin/process_macos.cc
index ae0f37e749462c0aba80502078bb43b03eb8b5d8..e369b215a5c4c92b8fa9c7df9e1efa43f42ad487 100644
--- a/runtime/bin/process_macos.cc
+++ b/runtime/bin/process_macos.cc
@@ -739,6 +739,10 @@ intptr_t Process::SetSignalHandler(intptr_t signal) {
     struct sigaction act;
     bzero(&act, sizeof(act));
     act.sa_handler = SignalHandler;
+    sigemptyset(&act.sa_mask);
+    for (int i = 0; i < kSignalsCount; i++) {
+      sigaddset(&act.sa_mask, kSignals[i]);
+    }
     int status = TEMP_FAILURE_RETRY_BLOCK_SIGNALS(
         sigaction(signal, &act, NULL));
     if (status < 0) {