fn main() {
    let output = std::process::Command::new("rustc")
        .arg("--version")
        .output()
        .expect("Failed to run rustc --version");
    let full = String::from_utf8(output.stdout).unwrap();
    // "rustc 1.79.0 (129f3b996 2024-06-10)" → "1.79.0"
    let version = full
        .trim()
        .trim_start_matches("rustc ")
        .split_whitespace()
        .next()
        .unwrap_or("unknown")
        .to_string();
    println!("cargo:rustc-env=RUSTC_VERSION={}", version);
    // Expose the build target triple so selfupdate can match release assets.
    println!(
        "cargo:rustc-env=BUILD_TARGET={}",
        std::env::var("TARGET").unwrap_or_default()
    );
    println!("cargo:rerun-if-changed=build.rs");
}