cmd/init: add missing library
cmd/init: add missing library

`perror` (which we use) comes from `stdio.h` (which we missed).

Signed-off-by: Ciro S. Costa <4f5054ab2db051d03adf9068233a850c82b24437@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse