arch: Clone jail object for serial.
arch: Clone jail object for serial.

80690665b8d745567e790e7b9fdd8742ba4c8a73 removed the clone but that
caused sig11 in minijail.

BUG=b:238026909
TEST=tast run rammus-arc-r arc.Boot.vm

Change-Id: Icf887ae62df682d72f2ea469a1d1a15cc303dc1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3744902
Reviewed-by: David Riley <a1c52a99f156ff41f0ea478f29291144551a02f6@chromium.org>
Reviewed-by: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Junichi Uekawa <6bd240a6ce32463e272bb69c685a8e946b33ac05@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm