rust/chg/build.rs

typing: add explicit hints for recent pytype regressions

Somewhere between 454feddab720 and cd72a88c5599, pytype changed how it inferred
the return type in `extdiff.py` from

    Tuple[Any, List[Tuple[bytes, Any, os.stat_result]]]

to

    Tuple[Any, List[nothing]]

It also changed the return type in `archival.py` from `Any` to `NoReturn`.  Fix
those up, and also the obvious parameter types while we're here.

fn main() {
    cc::Build::new()
        .warnings(true)
        .file("src/sendfds.c")
        .file("src/sighandlers.c")
        .compile("procutil");
}