yocto: Updated scons build configuration for Yocto

yocto: Updated scons build configuration for Yocto

* Added i686 to the list of supported target architectures
  for a Yocto build.

Change-Id: I2b5b3191807ab7229cb3457f42a21a94a1d1611e
Signed-off-by: Kishen Maloor <kishen.maloor@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2873
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Habib Virji <habib.virji@samsung.com>
Author: Kishen Maloor <kishen.maloor@intel.com>
Origin: https://gerrit.iotivity.org/gerrit/#/c/2873/
Signed-off-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/12147
Reviewed-by: Ziran Sun <ziran.sun@samsung.com>