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-example/rust-part
    
    the code of the file until where you have to start completion: use flapigen::{CppConfig, CppOptional, CppStrView, CppVariant, LanguageConfig};
use std::{env, path::Path};

fn main() {
    let out_dir = env::var("OUT_DIR").expect("no OUT_DIR, but cargo should provide it");
    //ANCHOR: cpp_config
    let cpp_cfg = CppConfig::new(
        // ANCHOR: cpp_output
        Path::new("..").join("cpp-part").join("rust-api"),
        // ANCHOR_END: cpp_output
        "rust".into(),
    )
    .cpp_optional(CppOptional::Boost)
    .cpp_variant(CppVariant::Boost)
    .cpp_str_view(CppStrView::Boost);
    //ANCHOR_END: cpp_config
    let swig_gen = flapigen::Generator::new(LanguageConfig::CppConfig(cpp_cfg));
    swig_gen.expand(
        "c++-api-for-rust",
        // ANCHOR: rust_input
        Path::new("src/cpp_glue.rs.in"),
        // ANCHOR_END: rust_input

        // ANCHOR: rust_outp
    
fn main() {
    let out_dir = env::var("OUT_DIR").expect("no OUT_DIR, but cargo should provide it");
    //ANCHOR: cpp_config
    let cpp_cfg = CppConfig::new(
        // ANCHOR: cpp_output
        Path::new("..").join("cpp-part").join("rust-api"),
        // ANCHOR_END: cpp_output
        "rust".into(),
    )
    .cpp_optional(CppOptional::Boost)
    .cpp_variant(CppVariant::Boost)
    .cpp_str_view(CppStrView::Boost);
    //ANCHOR_END: cpp_config
    let swig_gen = flapigen::Generator::new(LanguageConfig::CppConfig(cpp_cfg));
    swig_gen.expand(
        "c++-api-for-rust",
        // ANCHOR: rust_input
        Path::new("src/cpp_glue.rs.in"),
        // ANCHOR_END: rust_input

        // ANCHOR: rust_output
        &Path::new(&out_dir).join("cpp_glue.rs"),
        // ANCHOR_END: rust_output
    );
    println!(
        "cargo:rerun-if-changed={}",
        Path::new("src").join("cpp_glue.rs.in").display()
    );
}