Coverity complains that we don't check for failures from dup()
and mkstemp(); add asserts that these syscalls succeeded.
Fixes: Coverity CID 1432516, 1432574
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20210525134458.6675-7-peter.maydell@linaro.org