[ROCm]: Add rocm as platform in export_harnessess_multi_platform_test

Author: Rahul Batra

tests/export_harnesses_multi_platform_test.py

@@ -136,9 +136,12 @@ def export_and_compare_to_native(
         if d.platform not in unimplemented_platforms
     ]
     logging.info("Using devices %s", [str(d) for d in devices])
-    # lowering_platforms uses "cuda" instead of "gpu"
+    # lowering_platforms uses "cuda" or "rocm" instead of "gpu"
+    gpu_platform = "cuda"
+    if jtu.is_device_rocm():
+        gpu_platform = "rocm"
     lowering_platforms: list[str] = [
-        p if p != "gpu" else "cuda"
+        p if p != "gpu" else gpu_platform
         for p in ("cpu", "gpu", "tpu")
         if p not in unimplemented_platforms
     ]