MPS make-thread (was: MPS: profiler)

[Helmut Eller]

> Just make-thread.
> (I am not sure if it is related; if not, I'd better try to prepare a
> reproducer later and start a new email thread)

This crashes for me:

  emacs -Q -batch -eval \
   '(thread-join (make-thread (lambda () (igc--collect))))'