cp --sparse=auto doesn't create a sparse file #6129
Description
The default coreutils cp behaviour uses standard fs copy as fallback when cow is not available in our filesystem.
Steps to reproduce issue
printf hello > a
./target/release/coreutils cp --sparse=auto a b
du -h b
12K b
du -h --apparent-size b
11K b
The correct cp behavior
printf hello > a
/usr/bin/cp --sparse=auto a b
du -h b
4.0K b
du -h --apparent-size b
11K b```