Fix generated native coverage launcher

Author: timfel

mx.graalpython/mx_graalpython.py

@@ -1037,9 +1037,9 @@ def graalvm_vm_arg(java_arg):
                         new_args[2] = "{exe_arg}";
                         {extra_args_c}
                         for (int i = 1; i < argc; i++) {{
-                            new_args[i + 3 + {len(agent_args_list)}] = argv[i];
+                            new_args[i - 1 + 3 + {len(agent_args_list)}] = argv[i];
                         }}
-                        new_args[argc + 3 + {len(agent_args_list)}] = NULL;
+                        new_args[argc - 1 + 3 + {len(agent_args_list)}] = NULL;
                         execvp("{original_launcher}", new_args);
                         perror("execvp failed");
                         return 1;