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/serde_derive
    
    the code of the file until where you have to start completion: use std::env;
use std::process::Command;
use std::str;

// 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 executing our build script.
fn main() {
    let minor = match rustc_minor_version() {
        Some(minor) => minor,
        None => return,
    };

    // Underscore const names stabilized in Rust 1.37:
    // https://blog.rust-lang.org/2019/08/15/Rust
    
fn main() {
    let minor = match rustc_minor_version() {
        Some(minor) => minor,
        None => return,
    };

    // Underscore const names stabilized in Rust 1.37:
    // https://blog.rust-lang.org/2019/08/15/Rust-1.37.0.html#using-unnamed-const-items-for-macros
    if minor >= 37 {
        println!("cargo:rustc-cfg=underscore_consts");
    }

    // The ptr::addr_of! macro stabilized in Rust 1.51:
    // https://blog.rust-lang.org/2021/03/25/Rust-1.51.0.html#stabilized-apis
    if minor >= 51 {
        println!("cargo:rustc-cfg=ptr_addr_of");
    }
}