rust/chg/build.rs

crecord: null out the curses attribute with `None` on failure to import

Pytype got really confused that this could be `Union[module, bool]`, and spewed
about tons of attributes that are not available on `bool`.

Differential Revision: https://phab.mercurial-scm.org/D10210

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