Function which::which_in

pub fn which_in<T, U, V>(
    binary_name: T, 
    paths: Option<U>, 
    cwd: V
) -> Result<PathBuf, &'static str> where
    T: AsRef<OsStr>,
    U: AsRef<OsStr>,
    V: AsRef<Path>, 

Find binary_name in the path list paths, using cwd to resolve relative paths.