When using `runCommandLocal`, clients are required to download imagemagick
and the source files, even if the theme is already available from a binary
cache.
This means that the OEM logo can be used to have a seamless boot process.
(Copy it in PNG format from /sys/firmware/acpi/bgrt/image)
The width of the progress bar will be adjusted to suit the width of the logo.
There is now a choice to either follow the main theme or keep a black
background.
systemd-boot enables the black background by default, as it always has a
black background itself, and keeping the same colour throughout the
whole boot process looks cleaner than applying our theme at the first
opportunity.
