Rephrase warnings when building with the cli

Signed-off-by: Ulysses Souza <[email protected]>

compose/project.py

@@ -368,9 +368,11 @@ class Project(object):
         if cli:
             log.warning("Native build is an experimental feature and could change at any time")
             if parallel_build:
-                log.warning("unavailable --parallel on COMPOSE_NATIVE_BUILDER=1")
+                log.warning("Flag '--parallel' is ignored when building with "
+                            "COMPOSE_NATIVE_BUILDER=1")
             if gzip:
-                log.warning("unavailable --compress on COMPOSE_NATIVE_BUILDER=1")
+                log.warning("Flag '--compress' is ignored when building with "
+                            "COMPOSE_NATIVE_BUILDER=1")
 
         def build_service(service):
             service.build(no_cache, pull, force_rm, memory, build_args, gzip, rm, silent, cli, progress)