don't emit rerun-if-changed when vendoring

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

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

    // rerun-if-changed causes openssl-sys to rebuild if the openssl include

    // dir has changed since the last build. However, this causes a rebuild

    // every time when vendoring so we disable it.

    #[cfg(not(feature = "vendored"))]

    if let Some(printable_include) = include_dir.join("openssl").to_str() {

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

    }