selftests/clone3: Fix broken test under !CONFIG_TIME_NS

selftests/clone3: Fix broken test under !CONFIG_TIME_NS

commit fc7f04dc23db50206bee7891516ed4726c3f64cf upstream.

When execute the following command to test clone3 under !CONFIG_TIME_NS:

  # make headers && cd tools/testing/selftests/clone3 && make && ./clone3

we can see the following error info:

  # [7538] Trying clone3() with flags 0x80 (size 0)
  # Invalid argument - Failed to create new process
  # [7538] clone3() with flags says: -22 expected 0
  not ok 18 [7538] Result (-22) is different than expected (0)
  ...
  # Totals: pass:18 fail:1 xfail:0 xpass:0 skip:0 error:0

This is because if CONFIG_TIME_NS is not set, but the flag
CLONE_NEWTIME (0x80) is used to clone a time namespace, it
will return -EINVAL in copy_time_ns().

If kernel does not support CONFIG_TIME_NS, /proc/self/ns/time
will be not exist, and then we should skip clone3() test with
CLONE_NEWTIME.

With this patch under !CONFIG_TIME_NS:

  # make headers && cd tools/testing/selftests/clone3 && make && ./clone3
  ...
  # Time namespaces are not supported
  ok 18 # SKIP Skipping clone3() with CLONE_NEWTIME
  ...
  # Totals: pass:18 fail:0 xfail:0 xpass:0 skip:1 error:0

Link: https://lkml.kernel.org/r/1689066814-13295-1-git-send-email-yangtiezhu@loongson.cn
Fixes: 515bddf0ec41 ("selftests/clone3: test clone3 with CLONE_NEWTIME")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>