do_common_tools is a mode specifier, it is on when we want tools and off
when we do not want tools.  It is intended to be flipped by the bootstrap
modes.  Whether those common tools are actually built is determined by
whether we are calling binary or binary-arch not related to whether we
want those packages to have content.

Enable this unconditionally.  This allows us to build the indep packages
on any arch is needed.
Signed-off-by: Andy Whitcroft <apw@canonical.com>