
Add the environment variable CENGN_STRATEGY for supporting CENGN. Set the default value to 'cengn_first', and we also can set the value to the other three value 'cengn', 'upstream' or 'upstream_first'. Story: 2008862 Task: 44361 Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com> Change-Id: I0326da798e808dce1b6fefd49e54f54ca41e8bcd