Constant marlu::built_info::RUSTDOC_VERSION

pub const RUSTDOC_VERSION: &str = r"rustdoc 1.80.0-nightly (867900499 2024-05-23)";

The output of /opt/rustwide/rustup-home/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustdoc -V; empty string if /opt/rustwide/rustup-home/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustdoc -V failed to execute