[ROCm][CI][Bugfix] Fixing the Multi-Modal Models Test (Extended) 1 group (#30013)

Signed-off-by: Andreas Karatzas <akaratza@amd.com>

tests/models/multimodal/pooling/conftest.py

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Pytest configuration for vLLM pooling tests."""
+
+import os
+import warnings
+
+from vllm.platforms import current_platform
+
+
+def pytest_collection_modifyitems(config, items):
+    """Set FLEX_ATTENTION backend for SigLIP tests on ROCm."""
+    if not current_platform.is_rocm():
+        return
+
+    siglip_tests = [item for item in items if "test_siglip" in item.nodeid]
+
+    if siglip_tests:
+        os.environ["VLLM_ATTENTION_BACKEND"] = "FLEX_ATTENTION"
+        warnings.warn(
+            "ROCm: Set VLLM_ATTENTION_BACKEND=FLEX_ATTENTION for SigLIP tests",
+            UserWarning,
+            stacklevel=1,
+        )