only rebuild if the openssl include changes, not any include

    let target = env::var("TARGET").unwrap();

    let (lib_dirs, include_dir) = find_openssl(&target);

    if let Some(printable_include) = include_dir.to_str() {

    let mut ossl_include_dir = include_dir.clone();

    ossl_include_dir.push("openssl");

    if let Some(printable_include) = ossl_include_dir.to_str() {

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

    }