bazel: use local spawn_strategy (#379)
bazel: use local spawn_strategy (#379)

According to Bazel's [docs](https://docs.bazel.build/versions/master/user-manual.html#flag--spawn_strategy), `standalone` is deprecated, and `local` is now preferred.

Signed-off-by: Michael Rebello <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@michaelrebello.com>
envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile