apt in trisquel aramo is neither `Build-Essential: yes` nor `Priority: required`,
causing it not being pulled when creating a buildd chroot. Since the
build-essential package includes all packages that are `Build-Essential: yes`,
use build-essential instead.

Also, the `trisquel-common` script is not referred to or run by any other
programs, so it's useless. Remove it.

Fixes: 76a9f47e
Fixes: a75b1ffc
Signed-off-by: Jing Luo <jing@jing.rocks>