guile: workaround ice ssa corruption while DEBUG_BUILD

guile: workaround ice ssa corruption while DEBUG_BUILD

Add:
MACHINE = "qemux86-64"
DEBUG_BUILD = "1"
to local.conf and there was a ssa corruption to build guile:
..
Unable to coalesce ssa_names 48 and 3476 which are marked as MUST COALESCE.
sp_48(ab) and  sp_3476(ab)
guile-2.0.11/libguile/vm-engine.c: In function 'vm_debug_engine':
guile-2.0.11/libguile/vm.c:673:19: internal compiler error: SSA corruption
 #define VM_NAME   vm_debug_engine
                   ^
guile-2.0.11/libguile/vm-engine.c:39:1: note: in expansion of macro 'VM_NAME'
 VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
 ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
...

Tweak libguile/vm-i-system.c to check the value of nshuf to workaround it.
The tweak didn't change previous logic.

[YOCTO #6411]

(From OE-Core rev: 3470bbf4ae178479bd090d7191d6f0469f154b0d)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>