[Tests] Fix LongRefcounting test.

We were retaining one too many times in the two `_DeathTest` tests,
which caused the tests to fail.  This was previously masked by a bug.

rdar://124212794

Author: al45tair

stdlib/public/runtime/RefCount.cpp

@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include <cstdio>
+
 #include "swift/Runtime/HeapObject.h"
 
 namespace swift {

unittests/runtime/LongTests/LongRefcounting.cpp

@@ -282,7 +282,7 @@ TEST(LongRefcountingTest, unowned_retain_overflow_DeathTest) {
   auto object = allocTestObject(&deinited, 1);
 
   // URC is 1. Retain to maxURC, then retain again and verify overflow error.
-  unownedRetainALot<true>(object, maxURC);
+  unownedRetainALot<true>(object, maxURC - 1);
   EXPECT_EQ(0u, deinited);
   EXPECT_ALLOCATED(object);
   ASSERT_DEATH(swift_unownedRetain(object),
@@ -329,7 +329,7 @@ TEST(LongRefcountingTest, nonatomic_unowned_retain_overflow_DeathTest) {
   auto object = allocTestObject(&deinited, 1);
 
   // URC is 1. Retain to maxURC, then retain again and verify overflow error.
-  unownedRetainALot<false>(object, maxURC);
+  unownedRetainALot<false>(object, maxURC - 1);
   EXPECT_EQ(0u, deinited);
   EXPECT_ALLOCATED(object);
   ASSERT_DEATH(swift_nonatomic_unownedRetain(object),