test: fix unreliable async-hooks/test-signalwrap

Use an interval to keep the event loop open so the test does not exit
before receiving all signals fom asynchronous `exec()` calls.
PR-URL: #17827Fixes: #14070
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

Author: Trott

test/async-hooks/test-signalwrap.js

@@ -1,7 +1,8 @@
 'use strict';
 constcommon=require('../common');
 
-if(common.isWindows)returncommon.skip('no signals in Windows');
+if(common.isWindows)
+common.skip('no signals in Windows');
 
 constassert=require('assert');
 constinitHooks=require('./init-hooks');
@@ -11,6 +12,10 @@ const exec = require('child_process').exec;
 consthooks=initHooks();
 
 hooks.enable();
+
+// Keep the event loop open so process doesn't exit before receiving signals.
+constinterval=setInterval(()=>{},9999);
+
 process.on('SIGUSR2',common.mustCall(onsigusr2,2));
 
 constas=hooks.activitiesOfTypes('SIGNALWRAP');
@@ -66,6 +71,7 @@ function onsigusr2() {
 }
 
 functiononsigusr2Again(){
+clearInterval(interval);
 setImmediate(()=>{
 checkInvocations(
 signal1,{init: 1,before: 2,after: 2,destroy: 1},