Always emit =thread-exited notifications, even if silent
[Note: the testcased added by this commit depends on
https://sourceware.org/pipermail/gdb-patches/2022-June/190259.html,
otherwise GDB just crashes when detaching the core]
Currently, in MI, =thread-created are always emitted, like:
=thread-group-started,id="i1",pid="195680"
=thread-created,id="1",group-id="i1"
...
but on teardown, if the target uses exit_inferior_silent, then you'll
only see the inferior exit notification (thread-group-exited), no
notification for threads.
The core target is one of the few targets that use
exit_inferior_silent. Here's an example session:
-target-select core $corefile
=thread-group-started,id="i1",pid="195680"
=thread-created,id="1",group-id="i1"
...
^connected,frame=....
(gdb)
-target-detach
=thread-group-exited,id="i1"
^done
(gdb)
This imbalance of emitting =thread-created but then not =thread-exited
seems off to me. (And, it complicates changes I want to do to
centralize emitting thread exit notifications for the CLI, which is
why I'm looking at this.)
And then, since most other targets use exit_inferior instead of
exit_inferior_silent, MI is already emitting =thread-exited
notifications when tearing down an inferior, for most targets.
This commit makes MI always emit the =thread-exited notifications,
even for exit_inferior_silent.
Afterwards, when debugging a core, MI outputs:
(gdb)
-target-detach
=thread-exited,id="1",group-id="i1" << new line
=thread-group-exited,id="i1"
^done
(gdb)
Surprisingly, there's no MI testcase debugging a core file. This
commit adds the first.
Change-Id: I5100501a46f07b6bbad3e04d120c2562a51c93a4