include! macro is what we were missing

[Rett Berg]

If we use include! we could remove the sub-crate pretty trivially:

https://blog.clap.rs/complete-me/#completionscriptgenerationinclap

// build.rs
extern crate clap;

use clap::Shell;

include!("src/cli.rs");

fn main() {  
    let mut app = build_cli();
    app.gen_completions("fake",          // We specify the bin name manually
                        Shell::Bash,      // Which shell to build completions for
                        env!("OUT_DIR")); // Where write the completions to
}

Basically the functions that we need can just be defined in files and then we can manaully include them for the build script -- removing the need of a sub-crate.