Function windows_link_status 

pub fn windows_link_status(
    copy_exists: bool,
    source: Option<&SourceFile>,
    running_exe: &Path,
    host: Host,
    version: &str,
) -> LinkStatus

The Windows rule on already-read inputs (pure, so it is tested on every platform): Stale when the .source path= differs from the running exe OR its version= differs from version.