Drat, Test/A05 still hanging sometimes

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

The interesting thing is where it is stuck.

The "runtests.zsh" thread is blocked on sigsuspend() in the "for file" loop,
waiting for the the $ZTST_exe thread to finish.

The $ZTST_exe thread is trying to exit -- in my case it is stuck on a mutex
with no zsh code left in the gdb-able call stack backtrace.

Strangely, though, if I kill that thread, the runtests thread also dies,
and the entire "make" aborts.  The "for file" loop is written in a way that
I would have expected runtests to simply continue on to the next pass.

I'm baffled.