[Fix] Use sys.executable instead of hardcoded python

Replace hardcoded "python" string with sys.executable to ensure
correct Python interpreter is used. This fixes failures on systems
with multiple Python runtimes or where "python" is not in PATH.

Similar to pytorch/pytorch#155918

torch/utils/benchmark/utils/valgrind_wrapper/timer_interface.py

@@ -640,7 +640,7 @@ class _ValgrindWrapper:
                         stat_log=stat_log,
                         bindings=self._bindings_module))
 
-                run_loop_cmd = ["python", script_file]
+                run_loop_cmd = [sys.executable, script_file]
             else:
                 if collect_baseline:
                     raise AssertionError("collect_baseline must be False for non-Python timers")