from config-4.8.0-1-grml-686:

CONFIG_64BIT=y
CONFIG_X86_64=y
CONFIG_X86=y
CONFIG_OUTPUT_FORMAT="elf64-x86-64"
To Reproduce:

wget http://daily.grml.org/grml32-small_sid/latest/grml32-small_sid_latest.iso

qemu-system-i386 -cdrom grml32-small_sid_latest.iso -m 1024 -vnc :0 -S -monitor 
stdio

same result for testing image:
http://daily.grml.org/grml32-small_testing/latest/grml32-
small_testing_latest.iso

Test with builds on 24th January 2017

Connect VNC viewer

type cont at (qemu) prompt in monitor.

Selection default option and receive:  

"""
This kernel requires an x86 64 CPU, but only detected an i686 CPU.
Unable to boot - please use a kernel appropriate for your CPU.
"""

see also https://www.yuri.org.uk/~murble/qemu-i386/vncscreenshot.png

Looking insde the testing image

file vmlinuz
vmlinuz: Linux kernel x86 boot executable bzImage, version 4.8.0-1-grml-686 
(team@grml.org) #1 Debian 4.8.15-1+grml.1 (201, RO-rootFS, swap_dev 0x3, Normal 
VGA 
 

 qemu-system-i386 -kernel vmlinuz -initrd initrd.img -m 1024 -vnc :0 -monitor 
stdio

"""
This kernel requires an x86 64 CPU, but only detected an i686 CPU.
Unable to boot - please use a kernel appropriate for your CPU.
"""