pep8

Signed-off-by: Justin Lecher <jlec@gentoo.org>
use coreutils's nproc, thanks Bircoph for the suggestion

Signed-off-by: Justin Lecher <jlec@gentoo.org>
if only one package exists, use that one

Signed-off-by: Justin Lecher <jlec@gentoo.org>
Add openrc implementation

Signed-off-by: Justin Lecher <jlec@gentoo.org>
Check for tool before usage

Signed-off-by: Justin Lecher <jlec@gentoo.org>