[llvm] [readtapi] Setup simple stubify support (PR #76075)

[Cyndy Ishida via llvm-commits]

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@@ -79,20 +92,65 @@ static void reportError(Twine Message, int ExitCode = EXIT_FAILURE) {
   exit(ExitCode);
 }
 
+/// Replace extension considering frameworks.
+static void replace_extension(SmallVectorImpl<char> &Path,
+                              const Twine &Extension) {
+  StringRef P(Path.begin(), Path.size());
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cyndyishida wrote:

Will do, I also am considering moving these filesystem helpers into `TextAPI`. 

https://github.com/llvm/llvm-project/pull/76075