rust/chg/build.rs

rust-format: update rustfmt version

This hasn't been updated in a while, and since we're updating the MSRV to
1.48.0, we might as well do this.

Differential Revision: https://phab.mercurial-scm.org/D11733

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