All of the examples look unreadable and hard to debug to me. Why not something like this rather than one massive nested instruction?

    let keys = Object.keys(envars);
    let text = keys.map(envar => `${envar}=${envars[envar]}`).join(" ");
    console.log(chalk.dim(`$ ${text}`), "node", args.join(' '));

That way you can easily inspect and verify the intermediate values at runtime. Helpful for you to see if your code works as expected, helpful for others to see what the code is doing.