[clang][Unit Test] Updating Negative Stat Caching Diagnostic Unit Test (llvm#138955)

This PR makes a minor modification to make it more stable. The only
change is adding a suffix to the path under test.

rdar://149147920
(cherry picked from commit 2017831)

Author: qiongsiwu

clang/unittests/Tooling/DependencyScanning/DependencyScanningFilesystemTest.cpp

@@ -154,12 +154,12 @@ TEST(DependencyScanningFilesystem, DiagnoseStaleStatFailures) {
   DependencyScanningFilesystemSharedCache SharedCache;
   DependencyScanningWorkerFilesystem DepFS(SharedCache, InMemoryFS);
 
-  bool Path1Exists = DepFS.exists("/path1");
+  bool Path1Exists = DepFS.exists("/path1.suffix");
   EXPECT_EQ(Path1Exists, false);
 
   // Adding a file that has been stat-ed,
-  InMemoryFS->addFile("/path1", 0, llvm::MemoryBuffer::getMemBuffer(""));
-  Path1Exists = DepFS.exists("/path1");
+  InMemoryFS->addFile("/path1.suffix", 0, llvm::MemoryBuffer::getMemBuffer(""));
+  Path1Exists = DepFS.exists("/path1.suffix");
   // Due to caching in SharedCache, path1 should not exist in
   // DepFS's eyes.
   EXPECT_EQ(Path1Exists, false);
@@ -168,5 +168,5 @@ TEST(DependencyScanningFilesystem, DiagnoseStaleStatFailures) {
       SharedCache.getInvalidNegativeStatCachedPaths(*InMemoryFS.get());
 
   EXPECT_EQ(InvalidPaths.size(), 1u);
-  ASSERT_STREQ("/path1", InvalidPaths[0].str().c_str());
+  ASSERT_STREQ("/path1.suffix", InvalidPaths[0].str().c_str());
 }