You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: build.rs
    path of file: ./repos/flapigen-rs/cpp_tests
    
    the code of the file until where you have to start completion: use std::{env, path::Path};

use flapigen::{CppConfig, CppOptional, CppStrView, CppVariant, LanguageConfig};

fn main() {
    env_logger::init();

    let out_dir = env::var("OUT_DIR").unwrap();

    let cpp_gen_path = Path::new("c++").join("rust_interface");
    let cpp_cfg = if cfg!(feature = "boost") {
        CppConfig::new(cpp_gen_path, "rust".into()).use_boost()
    } else {
        let mut cfg = CppConfig::new(cpp_gen_p
    
fn main() {
    env_logger::init();

    let out_dir = env::var("OUT_DIR").unwrap();

    let cpp_gen_path = Path::new("c++").join("rust_interface");
    let cpp_cfg = if cfg!(feature = "boost") {
        CppConfig::new(cpp_gen_path, "rust".into()).use_boost()
    } else {
        let mut cfg = CppConfig::new(cpp_gen_path, "rust".into())
            .cpp_optional(CppOptional::Boost)
            .cpp_variant(CppVariant::Boost)
            .cpp_str_view(CppStrView::Boost);
        if cfg!(feature = "cpp17_optional") {
            cfg = cfg.cpp_optional(CppOptional::Std17);
        }
        if cfg!(feature = "cpp17_variant") {
            cfg = cfg.cpp_variant(CppVariant::Std17);
        }
        if cfg!(feature = "cpp17_string_view") {
            cfg = cfg.cpp_str_view(CppStrView::Std17);
        }
        cfg
    };

    let swig_gen = flapigen::Generator::new(LanguageConfig::CppConfig(cpp_cfg))
        .rustfmt_bindings(true)
        .remove_not_generated_files_from_output_directory(true);
    let src = Path::new("src").join("cpp_glue.rs.in");
    swig_gen.expand(
        "flapigen_test_c++",
        &src,
        &Path::new(&out_dir).join("cpp_glue.rs"),
    );
    println!("cargo:rerun-if-changed={}", src.display());
}