test: fix flakyness with `yes.exe`

PR-URL: https://github.com/nodejs/node/pull/12821
Fixes: https://github.com/nodejs/node/issues/12817
Refs: https://github.com/nodejs/node/pull/12658
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/child_process/child-process-read.js

@@ -1,6 +1,11 @@
 'use strict';
 const common = require('../common.js');
+
+// This benchmark uses `yes` to a create noisy child_processes with varying
+// output message lengths, and tries to read 8GB of output
+
 const os = require('os');
+const child_process = require('child_process');
 
 var messagesLength = [64, 256, 1024, 4096];
 // Windows does not support that long arguments
@@ -12,7 +17,6 @@ const bench = common.createBenchmark(main, {
   dur: [5]
 });
 
-const spawn = require('child_process').spawn;
 function main(conf) {
   bench.start();
 
@@ -21,7 +25,7 @@ function main(conf) {
 
   const msg = '"' + Array(len).join('.') + '"';
   const options = { 'stdio': ['ignore', 'pipe', 'ignore'] };
-  const child = spawn('yes', [msg], options);
+  const child = child_process.spawn('yes', [msg], options);
 
   var bytes = 0;
   child.stdout.on('data', function(msg) {
@@ -29,7 +33,12 @@ function main(conf) {
   });
 
   setTimeout(function() {
-    child.kill();
+    if (process.platform === 'win32') {
+      // Sometimes there's a yes.exe process left hanging around on Windows...
+      child_process.execSync(`taskkill /f /t /pid ${child.pid}`);
+    } else {
+      child.kill();
+    }
     const gbits = (bytes * 8) / (1024 * 1024 * 1024);
     bench.end(gbits);
   }, dur * 1000);