bug#22809: qemu-image builds failing

[Mark H Weaver]

The qemu-image builds are failing on Hydra in a different way than I've
seen before.

  http://hydra.gnu.org/build/1045494
  http://hydra.gnu.org/build/1045589

Here's the tail of the x86_64 failure log:

--8<---------------cut here---------------start------------->8---
ERROR: In procedure copy-file:
ERROR: In procedure copy-file: Success

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
[  183.101757] Kernel panic - not syncing: Attempted to kill init! 
exitcode=0x00000000
[  183.101757] 
[  183.102353] CPU: 0 PID: 1 Comm: init Not tainted 4.4.2-gnu #1
[  183.102728] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
[  183.103438]  0000000000000000 000000002ad908f2 ffff88000e443e10 
ffffffff813b7424
[  183.103957]  ffffffff81aa7288 ffff88000e443e98 ffffffff811848b8 
ffff880000000010
[  183.104476]  ffff88000e443ea8 ffff88000e443e40 000000002ad908f2 
ffffffff8117d811
[  183.105248] Call Trace:
[  183.105529]  [<ffffffff813b7424>] dump_stack+0x44/0x60
[  183.105752]  [<ffffffff811848b8>] panic+0xd5/0x21c
[  183.105752]  [<ffffffff8117d811>] ? perf_event_exit_task+0xc1/0x370
[  183.105752]  [<ffffffff81080fd3>] do_exit+0xaa3/0xae0
[  183.105752]  [<ffffffff810a8a00>] ? wake_up_state+0x10/0x20
[  183.105752]  [<ffffffff81081095>] do_group_exit+0x45/0xb0
[  183.105752]  [<ffffffff81081114>] SyS_exit_group+0x14/0x20
[  183.105752]  [<ffffffff817df5f6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  183.105752] Kernel Offset: disabled
[  183.105752] ---[ end Kernel panic - not syncing: Attempted to kill init! 
exitcode=0x00000000
[  183.105752] 
building of `/gnu/store/snzkp8sv2f0ayr4xbmdx7bvhrclkb0ph-disk-image.drv' timed 
out after 3600 seconds of silence
@ build-failed /gnu/store/snzkp8sv2f0ayr4xbmdx7bvhrclkb0ph-disk-image.drv - 
timeout
guix build: error: build failed: build of 
`/gnu/store/snzkp8sv2f0ayr4xbmdx7bvhrclkb0ph-disk-image.drv' failed
--8<---------------cut here---------------end--------------->8---

      Mark