We always need proxy for build, so we always use "docker build" command instead of "make build", but now for some reasons, we need macro defined in Makefile, so it would be helpful if we can use "make build" without touching Dockerfile. Signed-off-by: Qiang Huang <h.huangqiang@huawei.com> Upstream-commit: d104ddb564b636631c82955e8a6749305e7afee8 Component: engine