allow '-jn' style option

[yaito3014]

allowing option like poac build -j8

should we consider poac build -rj8 as poac build --release --jobs 8?

[ken-matsui]

Just to confirm, does Cargo accept the same style?

[yaito3014]

clap accepts no-space variant, so does cargo.

[ken-matsui]

Thank you for working on this. It'd be great if you could implement this for other flags, preferably elegantly.

[ken-matsui]

Also, feel free to implement the -rj8 style if Cargo supports this likewise.