- update to 20.1:
* `BuildSources=` are now mounted when we install packages so
local packages can be made available in the sandbox.
* Fixed check to see if we're running as root which makes sure
we don't do shared mounts when running as root.
* The extension release file is now actually written when
building system or configuration extensions.
* The nspawn settings are copied to the output directory again.
* Incremental caching is now skipped when `Overlay=` is enabled
as this combination isn't supported.
* The SELinux relabel check is more granular and now checks for
all required files instead of just whether there's a policy
configured.
* `qemu-system-xxx` binaries are now preferred over the generic
`qemu` and `qemu-kvm` binaries.
* Grub tools from the tools tree are now used to install grub
instead of grub tools from the image itself. The grub tools
were added to the default tools trees as well.
* The pacman keyring in tools trees is now only populated from
the Arch Linux keyring (and not the Debian/Ubuntu ones anymore).
* `gpg` is allowed to access `/run/pscsd/pscsd.comm` on the
host if it exists to allow interaction with smartcards.
* The current working directory is not mounted unconditionally
to `/work/src` anymore. Instead, the default value for
`BuildSources=` now mounts the current working directory
to `/work/src`. This means that the current working directory
is no longer implicitly included when `BuildSources=` is
explicitly configured.
* Assigning the empty string to a setting that takes a list of
values now overrides any configured default value as well.