Install ninja in the build image used by CircleCI. (#1888)
Install ninja in the build image used by CircleCI. (#1888)

Signed-off-by: Piotr Sikora <ba6f3a1a6d7e1ecae91b31e93969cc392fbd0fdd@google.com>
lizan/proxy,istio/proxy,istio/proxy,lizan/proxy,lizan/proxy,lizan/proxy,istio/proxy,istio/proxy