[CI/Build] Use spawn subprocess for ROCm (#30272)

Signed-off-by: Ryan Rock <ryan.rock@amd.com>

examples/offline_inference/data_parallel.py

@@ -33,6 +33,7 @@ import os
 from time import sleep
 
 from vllm import LLM, SamplingParams
+from vllm.platforms import current_platform
 from vllm.utils.network_utils import get_open_port
 
 
@@ -222,6 +223,11 @@ if __name__ == "__main__":
 
     from multiprocessing import Process
 
+    if current_platform.is_rocm():
+        from multiprocessing import set_start_method
+
+        set_start_method("spawn", force=True)
+
     procs = []
     for local_dp_rank, global_dp_rank in enumerate(
         range(node_rank * dp_per_node, (node_rank + 1) * dp_per_node)