Support hardlink detection on Windows nightly

[topin89]

On nightly, there are function that are essentially Windows counterpart to ino and dev, file_index and volume_serial_number. The problem is, on directory walking, as opposed to getting metadata from a file directly, they return None, so I had to change logic of the inner loop as well as check_inode signature.

Next trouble was checking if nightly build or not. I had to use build.rs script to get this info.

Checked Windows and WSL build, all seems to work as expected, hardlinks are skipped on nightly build and considered dupes on stable.