I had a look at the errflag logic and admittedly I don't understand
everything/much. However I noticed that other
<https://github.com/zsh-users/zsh/blob/6d49734d46a66b572cf064f60dac8d9e0ad309d0/Src/exec.c#L1935>
places
<https://github.com/zsh-users/zsh/blob/6d49734d46a66b572cf064f60dac8d9e0ad309d0/Src/exec.c#L4598>
that restore the errflag preserve the ERRFLAG_INT bit. Maybe the same
should be done here, even though it may not be that important as we are on
the exit path anyway.

I also wondered whether signals.c/dotraps
<https://github.com/zsh-users/zsh/blob/6d49734d46a66b572cf064f60dac8d9e0ad309d0/Src/signals.c#L1456>
would
be a better place for the new logic. It already has special logic for
SIGEXIT and this way the new logic would be guaranteed to apply to all runs
of SIGEXIT.

Philippe