tools lib lk: Fix for cross build

tools lib lk: Fix for cross build

Currently, lib lk doesn't use CROSS_COMPILE environment variable, so
cross build always fails.

This is a quick fix for this problem.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1371603750-15053-2-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>