Make the write end of the interrupt pipe in the eventhandler blocking on mac and linux.

runtime/bin/eventhandler_macos.cc

Index: runtime/bin/eventhandler_macos.cc
diff --git a/runtime/bin/eventhandler_macos.cc b/runtime/bin/eventhandler_macos.cc
index cb75febb0c5ad6f7ddd1ea5d328f04573d9a36c5..0342745ea595cac4d75a3f703d49fdd8d1e4a7a8 100644
--- a/runtime/bin/eventhandler_macos.cc
+++ b/runtime/bin/eventhandler_macos.cc
@@ -60,7 +60,6 @@ EventHandlerImplementation::EventHandlerImplementation() {
     FATAL("Pipe creation failed");
   }
   FDUtils::SetNonBlocking(interrupt_fds_[0]);
-  FDUtils::SetNonBlocking(interrupt_fds_[1]);
   timeout_ = kInfinityTimeout;
   timeout_port_ = 0;
 }
@@ -106,9 +105,9 @@ void EventHandlerImplementation::WakeupHandler(intptr_t id,
   msg.dart_port = dart_port;
   msg.data = data;
   intptr_t result =
-    write(interrupt_fds_[1], &msg, kInterruptMessageSize);
+      FDUtils::WriteToBlocking(interrupt_fds_[1], &msg, kInterruptMessageSize);
   if (result != kInterruptMessageSize) {
-    perror("Interrupt message failure");
+    FATAL("Interrupt message failure");
   }
 }