Set entry type when adding to the tar file (#2859)

We need to explicitly set this because the header initializes with all
null bytes. When this is not set, the python `tarfile` module can fail
to process the file properly due to treating an entry of type `AREGTYPE`
that also ends in a trailing slash as a directory instead of a regular
file under some very specific circumstances.
See python/cpython#141707 for more details

Fixes #2855

Author: e-nomem

src/module_writer.rs

@@ -388,6 +388,7 @@ impl ModuleWriter for SDistWriter {
         }
 
         let mut header = tar::Header::new_gnu();
+        header.set_entry_type(tar::EntryType::Regular);
         header.set_size(bytes.len() as u64);
         header.set_mode(permissions);
         header.set_mtime(self.mtime);