[Clang] Fix `PPChainedCallbacks::EmbedFileNotFound()`#170293

cofibrant merged 3 commits intollvm:mainllvm/llvm-project:mainfrom

cofibrant:users/cofibrant/fix-chained-embed-file-not-found-callbackcofibrant/llvm-project:users/cofibrant/fix-chained-embed-file-not-found-callbackCopy head branch name to clipboard