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/phaser/phaser/vendor/futures-macro
    
    the code of the file until where you have to start completion: #![warn(rust_2018_idioms, single_use_lifetimes)]

use autocfg::AutoCfg;

// The rustc-cfg strings below are *not* public API. Please let us know by
// opening a GitHub issue if your build environment requires some way to enable
// these cfgs other than by executi
    
fn main() {
    let cfg = match AutoCfg::new() {
        Ok(cfg) => cfg,
        Err(e) => {
            println!(
                "cargo:warning={}: unable to determine rustc version: {}",
                env!("CARGO_PKG_NAME"),
                e
            );
            return;
        }
    };

    // Function like procedural macros in expressions patterns statements stabilized in Rust 1.45:
    // https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#stabilizing-function-like-procedural-macros-in-expressions-patterns-and-statements
    if cfg.probe_rustc_version(1, 45) {
        println!("cargo:rustc-cfg=fn_like_proc_macro");
    }

    println!("cargo:rerun-if-changed=build.rs");
}