Without this simply changing the number of threads via
PARALLEL_MAKE can invalidate sstate-cache
(From OE-Core rev: 45140c860272fa4b610805d4dacadcf9201c3e35)
Signed-off-by: Matthew McClintock <msm@freescale.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>