[clang] [llvm] [clang][DependencyScanner] Remove unused -ivfsoverlay files (PR #73734)

[Ben Langmuir via cfe-commits]

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@@ -498,11 +518,18 @@ class NamedNodeOrError {
 } // namespace detail
 
 /// An in-memory file system.
-class InMemoryFileSystem : public FileSystem {
+class InMemoryFileSystem : public RTTIExtends<InMemoryFileSystem, FileSystem> {
   std::unique_ptr<detail::InMemoryDirectory> Root;
   std::string WorkingDirectory;
   bool UseNormalizedPaths = true;
 
+public:
+  static const char ID;
+  using GetFileContentsCallback =
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benlangmuir wrote:

Is this callback type used?

https://github.com/llvm/llvm-project/pull/73734