Hi Guix!

I noticed linux 6.4 didn't build on aarch64
https://ci.guix.gnu.org/build/1787394/details, building it locally and
checking the log, it seems we're simply missing the `hexdump' column:

--8<---------------cut here---------------start------------->8---
  CC [M]  drivers/pci/controller/pcie-rockchip-host.mod.o
  OBJCOPY arch/arm64/boot/Image
  CC [M]  drivers/pci/controller/pcie-brcmstb.mod.o
  AS      arch/arm64/boot/zboot-header.o
make[1]: hexdump: No such file or directory
make[1]: hexdump: No such file or directory
make[1]: hexdump: No such file or directory
make[1]: hexdump: No such file or directory
  PAD     arch/arm64/boot/vmlinux.bin
  CC [M]  drivers/pci/controller/pcie-apple.mod.o
truncate: Invalid number: 'arch/arm64/boot/vmlinux.bin'
make[1]: *** [drivers/firmware/efi/libstub/Makefile.zboot:13: arch/arm64/boot/vmlinux.bin] Error 1
make[1]: *** Deleting file 'arch/arm64/boot/vmlinux.bin'
make: *** [arch/arm64/Makefile:163: vmlinuz.efi] Error 2
make: *** Waiting for unfinished jobs....
  CC [M]  drivers/pci/pci-stub.mod.o
  CC [M]  drivers/video/backlight/ams369fg06.mod.o
  CC [M]  drivers/video/backlight/lcd.mod.o
  CC [M]  drivers/video/backlight/hx8357.mod.o
--8<---------------cut here---------------end--------------->8---

The "PAD" line seems to come from this Makefile, imported in a few
targets: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/efi/libstub/Makefile.zboot#n7

So the fix is easy! Somebody probably already found the issue, but I
figure I'd post the fix in case it saves time :-)

Thanks!
Pierre