Stop relying on allocator behaviour in modules unit test

Another fixup for r355778 for Windows bots, this time to stop
accidentally relying on allocator behaviour for the test to pass.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@355780 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 59f2009)

unittests/Serialization/InMemoryModuleCacheTest.cpp

@@ -72,12 +72,15 @@ TEST(InMemoryModuleCacheTest, addBuiltPCM) {
 }
 
 TEST(InMemoryModuleCacheTest, tryToDropPCM) {
-  auto B = getBuffer(1);
-  auto *RawB = B.get();
+  auto B1 = getBuffer(1);
+  auto B2 = getBuffer(2);
+  auto *RawB1 = B1.get();
+  auto *RawB2 = B2.get();
+  ASSERT_NE(RawB1, RawB2);
 
   InMemoryModuleCache Cache;
   EXPECT_EQ(InMemoryModuleCache::Unknown, Cache.getPCMState("B"));
-  EXPECT_EQ(RawB, &Cache.addPCM("B", std::move(B)));
+  EXPECT_EQ(RawB1, &Cache.addPCM("B", std::move(B1)));
   EXPECT_FALSE(Cache.tryToDropPCM("B"));
   EXPECT_EQ(nullptr, Cache.lookupPCM("B"));
   EXPECT_EQ(InMemoryModuleCache::ToBuild, Cache.getPCMState("B"));
@@ -91,17 +94,13 @@ TEST(InMemoryModuleCacheTest, tryToDropPCM) {
   EXPECT_DEATH(Cache.finalizePCM("B"), "Trying to finalize a dropped PCM");
 #endif
 
-  B = getBuffer(2);
-  ASSERT_NE(RawB, B.get());
-  RawB = B.get();
-
   // Add a new one.
-  EXPECT_EQ(RawB, &Cache.addBuiltPCM("B", std::move(B)));
+  EXPECT_EQ(RawB2, &Cache.addBuiltPCM("B", std::move(B2)));
   EXPECT_TRUE(Cache.isPCMFinal("B"));
 
   // Can try to drop again, but this should error and do nothing.
   EXPECT_TRUE(Cache.tryToDropPCM("B"));
-  EXPECT_EQ(RawB, Cache.lookupPCM("B"));
+  EXPECT_EQ(RawB2, Cache.lookupPCM("B"));
 }
 
 TEST(InMemoryModuleCacheTest, finalizePCM) {