Bug/regression: tt(RANDOM) seed not updating when $RANDOM is used in a pipe

[Jon Oster <jon.i.oster@xxxxxxxxx>]

In 5.8.1, $RANDOM seems not to update its state when the command $RANDOM
was used in is piped somewhere. For example:

# echo $RANDOM
18163
# echo $RANDOM
23472
# echo $RANDOM
27685
# echo $RANDOM|cat
10178
# echo $RANDOM|cat
10178
# echo $RANDOM
10178
# echo $RANDOM
17862

This is new behaviour since I upgraded from 5.4.2 to 5.8.1. At first I
thought that it might be somehow related to multios, but the result is
the same with multios on or off. So, I did a bisect, and discovered that
faf0035e532cde45528806e7a05ad28a0ab7c0fb[1] is the commit that introduced
this behaviour.

Is this considered a bug? Or is it intended behaviour? Personally, I'd
argue it's a bug. Unfortunately, my C isn't good enough to try to fix and
submit a patch myself, but I tried to make this bug report as helpful as
possible.

[1] https://sourceforge.net/p/zsh/code/ci/faf0035e532cde45528806e7a05ad28a0ab7c0fb/