mkdir when destination directory doesn't exist (#9060)

Fixes #8980

Make sure we mkdir if destination directory doesn't exist. I have no
idea why it doesn't work before

ghstack-source-id: 745e02d
Pull Request resolved: #9055

Co-authored-by: Mengwei Liu <[email protected]>

Author: pytorchbot

setup.py

@@ -463,7 +463,8 @@ def build_extension(self, ext: _BaseExtension) -> None:
         dst_file: Path = ext.dst_path(self)
 
         # Ensure that the destination directory exists.
-        self.mkpath(os.fspath(dst_file.parent))
+        if not dst_file.parent.exists():
+            self.mkpath(os.fspath(dst_file.parent))
 
         # Copy the file.
         self.copy_file(os.fspath(src_file), os.fspath(dst_file))