This ensures a ".dtb" PE section makes it into the UKI so systemd-stub
can install the correct devicetree for use by the Linux kernel. This is
often needed on systems that boot with u-boot since the devicetree used
by u-boot is often a paired down version of what the Linux kernel needs.
On those kinds of boards, the lack of this PE section means that u-boot
will end up installing its internal devicetree into the UEFI
configuration table, which is what the Linux kernel ends up using.