root.sh: Add plymouth's default theme configuration

See merge request !165

Increase image sizes by 300M to compensate for bigger /boot partition

See merge request !167

conf/board: Increase the boot partition size to 512M

See merge request !166

Currently used 200M is too small to hold the kernels
before autoremoval logic has a chance to kick in.

Allow to build against Debian Bullseye too

See merge request !164

On PureOS Amber that is less of a concern since it's stable now (and we
could use pinning) and on bullseye we don't care yet

Update ci repo key

See merge request !163

I thought we'd get them but it's stored in the repo. This
will move into a deb package too.

Temporarily drop gnome-dev from x86 images

See merge request !162

It can't install due to

librem5-base!136

so let's drop that until the package migrated.

board: Adjust to branch rename

See merge request !161

The linux-next branch lost it's 'linux-' to avoid confusion
with upstream's linux-next tree.

Don't inherit MIRROR from environment

See merge request !158

Increase max size of image

See merge request !160

x86_64 qemu images are failing to build in Jenkins.

https://arm01.puri.sm/job/Images/job/Image%20Build/3568/console

    update-initramfs: Generating /boot/initrd.img-4.19.0-5-amd64
    cp: error writing '/var/tmp/mkinitramfs_urPgne//lib/udev/ata_id': No space left on device
    E: /usr/share/initramfs-tools/hooks/udev failed with return 1.
    update-initramfs: failed for /boot/initrd.img-4.19.0-5-amd64 with 1.
    dpkg: error processing package initramfs-tools (--configure):
     installed initramfs-tools package post-installation script subprocess returned error exit status 1

This commit increases the size of the virtual disk used to build the
image.

Don't inherit $MIRROR from the environment. $mirror gets overridden later
from sourced configuration in conf/dists/*

Don't try to run extlinux

See merge request !157

This does not exist on arm64 and it's not needed.

Explicitly install vmdebootstrap/qemu-user-static on Laniakea Spark instance

See merge request !156

build-image: Exit in case of an unknown dist

See merge request !155

When using the spark builder setup don't carry on if the dist
is unknown.

build-image: Fix spark build condition

See merge request !154

We want to do the setup if SPARK_ID is non-empty

Broken-by: 2db8dc7e

Install unzip in environments where it may be missing

See merge request !108

Add Debian bullseye

See merge request !148

No sshd

See merge request Librem5/image-builder!151

Otherwise we abort image generation due to lack of sshd.

Almost plain builds

See merge request Librem5/image-builder!150

This is supposed to build everything from the archive without
reaching out to external sources. This isn't true for uboot
yet though.

The m4.bin is already fetched in fetch_uboot().

This never worked since the fetched m4.bin is a zip archive
that was never uncompressed.

c2505d88 did only part of the job