Send SIGKILL instead of SIGTERM in watch.sh

[silverwind]

Should fix the issue mentioned in #24845 (comment).

[silverwind]

Actually, no, I still get processes disassocated with the shell, checking...

[wxiaoguang]

SIGKILL is not the right choice in most cases.

[silverwind]

Actually I can currently not reproduce the zombie processes anymore with the current command, so it may be fine already. Hitting CTRL-C will not wait on the processes to terminate, which may be the reason why I thought it leaves zombies, but actually does not.

FTR, this is what I worked out to kill the processes and all spawned children:

#!/bin/bash
set -euo pipefail

make --no-print-directory watch-frontend &
make --no-print-directory watch-backend &

function cleanup() {
  for PID in $(jobs -p); do
    kill $(pgrep -P $PID) $PID
  done
}
trap cleanup EXIT

wait