Explicitly flush stdout in 2033-shutdown-mechanics

We might have been losing output before. And this can't hurt.

Bug: 155098113
Test: testrunner.py --host -b -t 2033-shutdown-mechanics
Change-Id: I883ce778664856110caf66c20f0ccefac137b156
diff --git a/test/2033-shutdown-mechanics/native_shutdown.cc b/test/2033-shutdown-mechanics/native_shutdown.cc
index 784daa7..2b7546a 100644
--- a/test/2033-shutdown-mechanics/native_shutdown.cc
+++ b/test/2033-shutdown-mechanics/native_shutdown.cc
@@ -21,6 +21,8 @@
 
 #include "jni.h"
 
+#include <stdio.h>
+
 namespace art {
 
 static void MaybePrintTime() {
@@ -41,16 +43,19 @@
       found_shutdown = true;
       MaybePrintTime();
       printf("Saw RuntimeShutdownFunctions\n");
+      fflush(stdout);
     }
     if (!found_runtime_deleted && extEnv->IsRuntimeDeleted()) {
       found_runtime_deleted = true;
       MaybePrintTime();
       printf("Saw RuntimeDeleted\n");
+      fflush(stdout);
     }
     if (found_shutdown && found_runtime_deleted) {
       // All JNI calls should now get rerouted to SleepForever();
       (void) env->NewByteArray(17);
       printf("Unexpectedly returned from JNI call\n");
+      fflush(stdout);
       SleepForever();
     }
   }