bug#28768: guix system vm Failed to install GRUB (EFI)

[Oleg Pykhalov]

Hello Guix,

EFI bootloader configuration causes problems to test with 'system vm'
before 'reconfigure'.

To reproduce it replace default bootloader expression with following
snippet in gnu/system/examples/vm-image.tmpl

  (bootloader (bootloader-configuration
               (bootloader grub-efi-bootloader)
               (target "/boot/efi")))

--8<---------------cut here---------------start------------->8---
[    0.909226] EXT4-fs (vda1): mounted filesystem with ordered data mode. Opts: 
(null)
installing bootloader...
/gnu/store/b1kdjsmwkphwh06gcm2ym0d0zh5wf4gc-grub-efi-2.02/sbin/grub-install: 
error: 
/gnu/store/b1kdjsmwkphwh06gcm2ym0d0zh5wf4gc-grub-efi-2.02/lib/grub/i386-pc/modinfo.sh
 doesn't exist. Please specify --target or --directory.
ERROR: In procedure scm-error:
ERROR: failed to install GRUB (EFI)

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
GNU Guile 2.2.2
Copyright (C) 1995-2017 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> [    1.344109] tsc: Refined TSC clocksource calibration: 
3392.250 MHz
[    1.344677] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 
0x30e5b54dbe0, max_idle_ns: 440795272496 ns
  C-c C-c
--8<---------------cut here---------------end--------------->8---