benchmark: forcefully close processes

PR-URL: nodejs/node#43557
Fixes: nodejs/build#2968
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

benchmark/common.js

@@ -289,7 +289,13 @@ function formatResult(data) {
 function sendResult(data) {
   if (process.send) {
     // If forked, report by process send
-    process.send(data);
+    process.send(data, () => {
+      // If, for any reason, the process is unable to self close within
+      // a second after completing, forcefully close it.
+      setTimeout(() => {
+        process.exit(0);
+      }, 5000).unref();
+    });
   } else {
     // Otherwise report by stdout
     process.stdout.write(formatResult(data));