travis: add build statistics
travis: add build statistics

Inheriting buildstats-summary adds some sstate statistics
to each bitbake invocation.

Signed-off-by: Patrick Ohly <0fc9d825c622b2a5ac5160289c29f03654b10648@intel.com>

01org/meta-intel-iot-security,acornea/meta-intel-iot-security,acornea/meta-intel-iot-security,01org/meta-intel-iot-security,01org/meta-intel-iot-security,acornea/meta-intel-iot-security,acornea/meta-intel-iot-security,acornea/meta-intel-iot-security,01org/meta-intel-iot-security