Add a flag to control whether to initialize gloo (#29150)

python/paddle/distributed/fleet/launch.py

@@ -219,7 +219,7 @@ def launch_collective(args):
     global_envs = copy.copy(os.environ.copy())
     gloo_rendezvous_dir = tempfile.mkdtemp()
     # add gloo env
-    global_envs["PADDLE_WITH_GLOO"] = "1"
+    global_envs["PADDLE_WITH_GLOO"] = str(os.getenv("PADDLE_WITH_GLOO", "1"))
     global_envs["PADDLE_GLOO_RENDEZVOUS"] = "3"
     global_envs["PADDLE_GLOO_FS_PATH"] = gloo_rendezvous_dir