Add comment on native build and fix typo

Signed-off-by: Ulysses Souza <ulysses.souza@docker.com>

compose/cli/main.py

@@ -266,7 +266,7 @@ class TopLevelCommand(object):
             --build-arg key=val     Set build-time variables for services.
             --compress              Compress the build context using gzip.
             --force-rm              Always remove intermediate containers.
-            -m, --memory MEM        Sets memory limit for the build container.
+            -m, --memory MEM        Set memory limit for the build container.
             --no-cache              Do not use cache when building the image.
             --no-rm                 Do not remove intermediate containers after a successful build.
             --parallel              Build images in parallel.

compose/service.py

@@ -1810,6 +1810,10 @@ class _CLIBuilder(object):
             image_id = line.split(":")[1].strip()
         os.remove(iidfile)
 
+        # In case of `DOCKER_BUILDKIT=1`
+        # there is no success message already present in the output.
+        # Since that's the way `Service::build` gets the `image_id`
+        # it has to be added `manually`
         if not appear:
             yield json.dumps({"stream": "{}{}\n".format(magic_word, image_id)})