As we prepare a RISC-V installer image, we need to add 'riscv64' to the
supported UEFI architectures. This commit does so by setting values
for grub_name and grub_target.
Make sure curthooks do not discard APT preferences
Although APT preferences applied properly when running curtin
apt-config, we observed during a full installation using Subiquity that
the preferences would not be honored when installing packages from the
"packages" autoinstall section.
This happened because the installation of packages occur after running
curthooks. Curtooks call handle_apt with an almost empty configuration.
Therefore, we would overwrite the preferences by removing the
etc/apt/preferences.d/90curtin.pref file.
It is to be noted that the same behavior occurs for the APT proxy.
Fixed by not removing etc/apt/preferences.d/90curtin.pref when the
configuration does not contain APT preferences.
* primary reason for this is to generate the changelog with a real
DEBNAME/DEBEMAIL
* remove template debian/changelog.trunk
* assume debian version 0ubuntu1
* let dch manage the changelog file
