specify matching ssubcommand for verify and build

[vezenovm]

Related issue(s)

(If it does not already exist, first create a GitHub issue that describes the problem this Pull Request (PR) solves before creating the PR and link it here.)

Resolves #263

Description

Fixes verify cmd and adds allow-warnings to build cmd

Summary of changes

It seems that fetching args using our CLI crate now requires specifying the subcommand being matched before fetching any args for that subcommands.

let args = args.subcommand_matches("build").unwrap();
Only then can you do
let allow_warnings = args.is_present("allow-warnings");

Dependency additions / changes

(If applicable.)

Test additions / changes

(If applicable.)

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.

Additional context

(If applicable.)

[jfecher]

Thanks!