test: add test-benchmark-os

Add minimal test to confirm that os benchmarks run.

PR-URL: https://github.com/nodejs/node/pull/14951
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-benchmark-os.js

@@ -0,0 +1,20 @@
+'use strict';
+
+require('../common');
+
+// Minimal test for os benchmarks. This makes sure the benchmarks aren't
+// horribly broken but nothing more than that.
+
+const assert = require('assert');
+const fork = require('child_process').fork;
+const path = require('path');
+
+const runjs = path.join(__dirname, '..', '..', 'benchmark', 'run.js');
+const argv = ['--set', 'n=1',
+              'os'];
+
+const child = fork(runjs, argv);
+child.on('exit', (code, signal) => {
+  assert.strictEqual(code, 0);
+  assert.strictEqual(signal, null);
+});