fix one small bug, re-check exec, but still can not start new test due to sbi panic

kernel/exec.c

@@ -265,7 +265,7 @@ int execve(char *path, char **argv, char **envp)
 		copyout(pagetable, a1, (char *)uargv, (argc + 1) * sizeof(uint64)) < 0 ||
 		copyout(pagetable, sp, (char *)&argc, sizeof(uint64)) < 0)
 	{
-		__debug_warn("execve", "fail to copy argv/envp table into user stack\n");
+		__debug_warn("execve", "fail to copy argv/envp table into user stack\n");//
 		ret = -EINVAL;
 		goto bad;
 	}