test: isolate the no-version gfx-override test from a real /opt/rocm

tests/studio/install/test_rocm_support.py

@@ -1914,6 +1914,13 @@ class TestInstallShStructure:
         family_fn = _extract_sh_function_body(source, "_amd_arch_index_family_for_gfx")
         assert fn and probe_fn and family_fn
         with tempfile.TemporaryDirectory() as d:
+            # Neutralise the host's real ROCm: the version chain reads
+            # /opt/rocm/.info/version directly (no tool to shim), which resolves
+            # a tag on a real ROCm box and skips the no-version endpoint under
+            # test. Same path-substitution technique as the KFD topology tests.
+            fn = fn.replace(
+                "/opt/rocm/.info/version", Path(d, "no-rocm-version").as_posix()
+            )
             with open(os.path.join(d, "uname"), "w", encoding = "utf-8", newline = "\n") as f:
                 f.write('#!/bin/sh\ncase "${1:-}" in -m) echo x86_64 ;; *) echo Linux ;; esac\n')
             # Silence every ROCm version source, not just amd-smi: a dev box with