build: setting DOCKER_BUILDKIT environment variable to any non-empty string enables the use of buildkit
build: setting DOCKER_BUILDKIT environment variable to any non-empty string enables the use of buildkit

Signed-off-by: Tibor Vass <3f1326dff4d85ad4ec938fb33f64575ace96db26@docker.com>

thaJeztah/cli,docker/cli,cpuguy83/cli,docker/cli,cpuguy83/cli,thaJeztah/cli