test: avoid left behind child processes

Extend the Linux logic to all POSIX platforms in
test-child-process-exec-abortcontroller-promisified.

PR-URL: nodejs#46276
Fixes: nodejs/build#3154
Refs: nodejs#37518
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Beth Griggs <bethanyngriggs@gmail.com>
Reviewed-By: Ruy Adorno <ruyadorno@google.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-child-process-exec-abortcontroller-promisified.js

@@ -10,9 +10,9 @@ const invalidArgTypeError = {
   name: 'TypeError'
 };
 
-const waitCommand = common.isLinux ?
-  'sleep 2m' :
-  `${process.execPath} -e "setInterval(()=>{}, 99)"`;
+const waitCommand = common.isWindows ?
+  `${process.execPath} -e "setInterval(()=>{}, 99)"` :
+  'sleep 2m';
 
 {
   const ac = new AbortController();