[clang] Stop adjusting the module cache path (#102540)

This patch stops adjustments of the module cache path beyond what is
done in `ParseHeaderSearchArgs` (making it absolute and removing dots).
This enables more efficient implementation of the caching VFS in
#88800.

Author: jansvoboda11

clang/lib/Frontend/CompilerInstance.cpp

@@ -1659,9 +1659,8 @@ static void pruneModuleCache(const HeaderSearchOptions &HSOpts) {
   // Walk the entire module cache, looking for unused module files and module
   // indices.
   std::error_code EC;
-  SmallString<128> ModuleCachePathNative;
-  llvm::sys::path::native(HSOpts.ModuleCachePath, ModuleCachePathNative);
-  for (llvm::sys::fs::directory_iterator Dir(ModuleCachePathNative, EC), DirEnd;
+  for (llvm::sys::fs::directory_iterator Dir(HSOpts.ModuleCachePath, EC),
+       DirEnd;
        Dir != DirEnd && !EC; Dir.increment(EC)) {
     // If we don't have a directory, there's nothing to look into.
     if (!llvm::sys::fs::is_directory(Dir->path()))

clang/lib/Lex/HeaderSearch.cpp

@@ -267,7 +267,6 @@ std::string HeaderSearch::getCachedModuleFileNameImpl(StringRef ModuleName,
     return {};
 
   SmallString<256> Result(CachePath);
-  llvm::sys::fs::make_absolute(Result);
 
   if (HSOpts->DisableModuleHash) {
     llvm::sys::path::append(Result, ModuleName + ".pcm");