[BugFix][Diffusion] Add CPU LAPACK fallback for FlowUniPC (#5329)

Signed-off-by: akshatvishu <akshatnayak197@gmail.com>

tests/diffusion/models/cosmos3/test_cosmos3_pipeline.py

@@ -16,7 +16,6 @@ from PIL import Image
 from torch import nn
 
 from vllm_omni.diffusion.worker.request_batch import DiffusionRequestBatch
-from vllm_omni.platforms import current_omni_platform
 
 pytestmark = [pytest.mark.core_model, pytest.mark.cpu, pytest.mark.diffusion]
 
@@ -858,10 +857,6 @@ def test_flow_unipc_reuses_scheduler_and_forwards_each_request_shift(make_cosmos
     assert all(call["sigmas"] is None for call in scheduler.set_timesteps_calls)
 
 
-@pytest.mark.skipif(
-    current_omni_platform.is_rocm(),
-    reason="Pytorch shipped with vLLM does not built with LAPACK support",
-)
 def test_flow_unipc_reproducible_with_same_seed(make_cosmos3_pipeline) -> None:
     from vllm_omni.diffusion.models.schedulers.scheduling_flow_unipc_multistep import (
         FlowUniPCMultistepScheduler,