Fixes#179700
Simple fix, if we are in batch mode, don't go into an interactive
session after checking if there are commands to run.
Testing it is more tricky. I tried a shell test as I thought it would be
simplest. However to be able to FileCheck I had to pipe and the pipe
turns off the prompt because it's non-interactive. The prompt is the
thing that must not be printed.
So I've just spawned lldb as a subprocess. If it doesn't quit quickly
then something is wrong. The timeout is high not because it should
normally take that long, but because sometimes a process will get
stalled for a while and I don't want this to be flaky.
(though in theory it can get stalled for much longer than a minute)
If it does time out, the process will be cleaned up automatically. See
https://docs.python.org/3/library/subprocess.html#subprocess.run
> A timeout may be specified in seconds, it is internally
> passed on to Popen.communicate(). If the timeout expires,
> the child process will be killed and waited for.
1ff4b50380