'waf' supports only simple '-j' and fails when parallel make flags
contain extended options like '--load-average'.
Patch uses the method from 'boost.inc' to filter '-j'.
(From OE-Core rev: bc394e1dd229845a315a97704beca43fbb8976ee)
Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>