fn build_vendored()

in bindings/rust/extended/s2n-tls-sys/build.rs [85:162]
50 lines of code
7 McCabe index (conditional complexity)

fn build_vendored() {
    let libcrypto = Libcrypto::default();

    let mut build = builder(&libcrypto);

    build.files(include!("./files.rs"));

    // https://doc.rust-lang.org/cargo/reference/environment-variables.html
    // * OPT_LEVEL, DEBUG — values of the corresponding variables for the profile currently being built.
    // * PROFILE — release for release builds, debug for other builds. This is determined based on if
    //   the profile inherits from the dev or release profile. Using this environment variable is not
    //   recommended. Using other environment variables like OPT_LEVEL provide a more correct view of
    //   the actual settings being used.
    if env("OPT_LEVEL") != "0" {
        build.define("S2N_BUILD_RELEASE", "1");
        build.define("NDEBUG", "1");

        // build s2n-tls with LTO if supported
        if build.get_compiler().is_like_gnu() {
            build
                .flag_if_supported("-flto")
                .flag_if_supported("-ffat-lto-objects");
        }
    }

    let out_dir = PathBuf::from(env("OUT_DIR"));

    let features = FeatureDetector::new(&out_dir, &libcrypto);

    let mut feature_names = std::fs::read_dir("lib/tests/features")
        .expect("missing features directory")
        .flatten()
        .filter(|file| {
            let file = file.path();
            file.extension().map_or(false, |ext| ext == "c")
        })
        .map(|file| {
            file.path()
                .file_stem()
                .unwrap()
                .to_str()
                .unwrap()
                .to_string()
        })
        .collect::<Vec<_>>();

    feature_names.sort();

    for name in &feature_names {
        let is_supported = features.supports(name);
        eprintln!("{name}: {is_supported}");
        if is_supported {
            build.define(name, "1");

            // stacktraces are only available if execinfo is
            if name == "S2N_EXECINFO_AVAILABLE" && option_env("CARGO_FEATURE_STACKTRACE").is_some()
            {
                build.define("S2N_STACKTRACE", "1");
            }
        }
    }

    // don't spit out a bunch of warnings to the end user, since they won't really be able
    // to do anything with it
    build.warnings(false);

    build.compile("s2n-tls");

    // linking to the libcrypto is handled by the rust compiler through the
    // `extern crate aws_lc_rs as _;` statement included in the generated source
    // files. This is less brittle than manually linking the libcrypto artifact.

    // let consumers know where to find our header files
    let include_dir = out_dir.join("include");
    std::fs::create_dir_all(&include_dir).unwrap();
    std::fs::copy("lib/api/s2n.h", include_dir.join("s2n.h")).unwrap();
    println!("cargo:include={}", include_dir.display());
}