In order to prevent multiple instances of the script running at the same
time.
(From OE-Core rev: 96a194de890f7ef1e6e5e036b32848e0f9d1bcf5)
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>