Fix nob_needs_rebuild with open files in windows

[eduardomosko]

Windows sucks

But anyway, I need to check if an exe needs_rebuild while it is running because of hot-reload reasons, and it won't work with GENERIC_READ.

As per https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea changing that to 0 works for querying the modification time.

If this parameter is zero, the application can query certain metadata such as file, directory, or device attributes without accessing that file or device, even if GENERIC_READ access would have been denied.

So yeah, accept this if you want.