[clang] NFCI: Use FileEntryRef::getName() in clangIndexSerialization

The clangIndexSerialization target seems to be unused, so it didn't build when I ran `check-all` before landing d1f86c3. This should resolve the deprecation warning that caused some build bots to fail.

Author: jansvoboda11

clang/include/clang/IndexSerialization/SerializablePathCollection.h

@@ -110,7 +110,7 @@ class SerializablePathCollection {
 
   /// Stores path to \p FE if it hasn't been stored yet.
   /// \returns index to array exposed by getPathsBuffer().
-  size_t tryStoreFilePath(const clang::FileEntry &FE);
+  size_t tryStoreFilePath(FileEntryRef FE);
 
 private:
   /// Stores \p Path if it is non-empty.

clang/lib/IndexSerialization/SerializablePathCollection.cpp

@@ -45,16 +45,16 @@ SerializablePathCollection::SerializablePathCollection(
       SysRootPath(Paths.addDirPath(SysRoot)),
       OutputFilePath(Paths.addDirPath(OutputFile)) {}
 
-size_t SerializablePathCollection::tryStoreFilePath(const FileEntry &FE) {
-  auto FileIt = UniqueFiles.find(&FE);
+size_t SerializablePathCollection::tryStoreFilePath(FileEntryRef FE) {
+  auto FileIt = UniqueFiles.find(FE);
   if (FileIt != UniqueFiles.end())
     return FileIt->second;
 
   const auto Dir = tryStoreDirPath(sys::path::parent_path(FE.getName()));
   const auto FileIdx =
       Paths.addFilePath(Dir.Root, Dir.Path, sys::path::filename(FE.getName()));
 
-  UniqueFiles.try_emplace(&FE, FileIdx);
+  UniqueFiles.try_emplace(FE, FileIdx);
   return FileIdx;
 }