test: add Unicode characters regression test

This test ensures that UTF-8 characters can be used in core JavaScript
modules built into Node's binary.

Refs: nodejs#11129

lib/internal/test/unicode.js

@@ -0,0 +1,6 @@
+'use strict';
+
+// This module exists entirely for regression testing purposes.
+// See `test/parallel/test-internal-unicode.js`.
+
+module.exports = '✓';

node.gyp

@@ -97,6 +97,7 @@
       'lib/internal/readline.js',
       'lib/internal/repl.js',
       'lib/internal/socket_list.js',
+      'lib/internal/test/unicode.js',
       'lib/internal/url.js',
       'lib/internal/util.js',
       'lib/internal/v8_prof_polyfill.js',

test/parallel/test-internal-unicode.js

@@ -0,0 +1,12 @@
+'use strict';
+require('../common');
+
+// Flags: --expose-internals
+//
+// This test ensures that UTF-8 characters can be used in core JavaScript
+// libraries built into Node's binary.
+
+const assert = require('assert');
+const character = require('internal/test/unicode');
+
+assert.strictEqual(character, '✓');