Add extra debug information when failing to deliver an interrupt message.

runtime/bin/eventhandler_linux.cc

Index: runtime/bin/eventhandler_linux.cc
diff --git a/runtime/bin/eventhandler_linux.cc b/runtime/bin/eventhandler_linux.cc
index 69551df9724a79a19d1885858fb0cac8f17f99cf..e98ffa042e31b596e4d2431e71fc6aeaa7d2e1f7 100644
--- a/runtime/bin/eventhandler_linux.cc
+++ b/runtime/bin/eventhandler_linux.cc
@@ -95,7 +95,10 @@ void EventHandlerImplementation::WakeupHandler(intptr_t id,
   intptr_t result =
       FDUtils::WriteToBlocking(interrupt_fds_[1], &msg, kInterruptMessageSize);
   if (result != kInterruptMessageSize) {
-    FATAL("Interrupt message failure");
+    if (result == -1) {
+      perror("Interrupt message failure:");
+    }
+    FATAL1("Interrupt message failure. Wrote %d bytes.", result);
   }
 }