This speeds up docker build time drastically. It still possible to
disable this by setting `DOCKER_INCREMENTAL_BUILD` to `0` (and this is
what should be done on the CI).
Signed-off-by: Vincent Demeester <vincent@sbr.pm>
Upstream-commit: 2c342cff79d6e781e06258cefcd2b2b1a23396ec
Component: engine