Remove dependencies to Aptitude

prepare-runtime specific code can be done in a pre_apt_script.
Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>

flatdeb/prepare-runtime

@@ -69,17 +69,5 @@ install -d \
 "$sysroot/var/lock" \
 ${NULL}
 
-# We use aptitude to help prepare the Platform runtime, and
-# it's a useful thing to have in the Sdk runtime
-in_chroot apt-get -q -y --no-install-recommends install aptitude
-
-# All packages will be removed from the platform runtime
-# unless they are Essential, depended-on, or in the
-# add_packages list.
-in_chroot aptitude -y markauto '?installed'
-
-# Ubuntu precise doesn't like apt being up for autoremoval.
-in_chroot aptitude -y unmarkauto apt
-
 # Required for openjdk-8-jre-headless
 install -d "$sysroot/usr/share/man/man1"