floss: Rerun topshim bindgen if underlying C++ code changes

    let bt_searches =

        paths.iter().map(|tail| format!("-I{}{}", search_root, tail)).collect::<Vec<String>>();

    // Also re-run the build if anything in the C++ build changes

    for path in bt_searches.iter() {

        println!("cargo:rerun-if-changed={}", path);

    }

    // "-x" and "c++" must be separate due to a bug

    let clang_args: Vec<&str> = vec!["-x", "c++", "-std=c++17"];