Merge pull request #8518 from z2oh/z2oh/cherrypick-fix-windows-fs-access-release-6.0

[cherrypick swift/release/6.0] Return `errc::no_such_file_or_directory` in `fs::access` if `GetFileAttributesW` fails

Author: DougGregor

llvm/lib/Support/Windows/Path.inc

@@ -630,6 +630,10 @@ std::error_code access(const Twine &Path, AccessMode Mode) {
   DWORD Attributes = ::GetFileAttributesW(PathUtf16.begin());
 
   if (Attributes == INVALID_FILE_ATTRIBUTES) {
+    // Avoid returning unexpected error codes when querying for existence.
+    if (Mode == AccessMode::Exist)
+      return errc::no_such_file_or_directory;
+
     // See if the file didn't actually exist.
     DWORD LastError = ::GetLastError();
     if (LastError != ERROR_FILE_NOT_FOUND && LastError != ERROR_PATH_NOT_FOUND)