Bug#958461: grub-install needs to be built with efivar support for armhf

[Steve McIntyre]

Source: grub2
Version: 2.02+dfsg1-20
Severity: important

Just had a bug reported via irc, and I've confirmed it myself. When
trying to install an armhf EFI system, grub-install complains and
aborts:

GRUB was not built with efivar support; cannot register EFI boot entry

While ARMv7 EFI is not common in hardware, this is important for armhf
VMs where EFI is the easiest way to configure them.

-- System Information:
Debian Release: 10.3
  APT prefers stable-debug
  APT policy: (500, 'stable-debug'), (500, 'stable'), (500, 'oldstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-8-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB:en (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled