[BUG] pipeline that cannot be interrupted with Ctrl-C (regression)

[Vincent Lefevre <vincent@xxxxxxxxxx>]

With zsh 5.7.1 under Debian, the following pipeline cannot be
interrupted with Ctrl-C:

  { /bin/sleep 10 ; /bin/sleep 20; } | { /bin/sleep 30 ; /bin/sleep 40; }

But if I remove one of the sleep, it can be interrupted by Ctrl-C.

There was no issue with zsh 5.3.1 (Debian 9).

Note: I mentioned this example in zsh-users in the thread
"kill the LHS command of a pipe once the RHS command terminates".

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Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)