print information about --noaudit when calling /usr/bin/cargo-ebuild --help

[stefson]

/usr/bin/cargo-ebuild defaults to fetching data for audit, to warn about vulnerable crates.

While this is a good thing I believe, it can cause tricky to debug segfaults as reported in #20 , or just flake with an error.

Trying to learn more about this feature via /usr/bin/cargo-ebuild --help doesn't give much of an result:

/usr/bin/cargo-ebuild --help
cargo-ebuild 0.5.0
Doug Goldstein <cardoe@cardoe.com>
Generates an ebuild for a given Cargo project

USAGE:
    cargo <SUBCOMMAND>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

SUBCOMMANDS:
    ebuild    Generates an ebuild for a given Cargo project
    help      Prints this message or the help of the given subcommand(s)

and /usr/bin/cargo ebuild --help shows the option, but without any informations:

/usr/bin/cargo ebuild --help
cargo-ebuild 0.5.0
Generates an ebuild for a given Cargo project

USAGE:
    cargo ebuild [FLAGS] [OPTIONS]

FLAGS:
    -h, --help       Prints help information
        --noaudit    
    -V, --version    Prints version information

OPTIONS:
        --package-name <PACKAGE>      Desired package name from cargo workspace
        --manifest-path <PATH>        Path to Cargo.toml
    -T, --template-path <TEMPLATE>    Non-standard template

so maybe you can add a few lines to the code with short info, what this flag actually does for the user.