test: remove unused common.libDir

PR-URL: #9124
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

test/README.md

@@ -271,11 +271,6 @@ Platform check for Windows 32-bit on Windows 64-bit.
 
 Checks whether any globals are not on the `knownGlobals` list.
 
-### libDir
-* return [<String>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type)
-
-Path to the 'lib' directory.
-
 ### localhostIPv4
 * return [<String>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type)
 

test/common.js

@@ -1,10 +1,10 @@
 /* eslint-disable required-modules */
 'use strict';
-var path = require('path');
-var fs = require('fs');
-var assert = require('assert');
-var os = require('os');
-var child_process = require('child_process');
+const path = require('path');
+const fs = require('fs');
+const assert = require('assert');
+const os = require('os');
+const child_process = require('child_process');
 const stream = require('stream');
 const util = require('util');
 const Timer = process.binding('timer_wrap').Timer;
@@ -14,7 +14,6 @@ const testRoot = process.env.NODE_TEST_DIR ?
 
 exports.testDir = __dirname;
 exports.fixturesDir = path.join(exports.testDir, 'fixtures');
-exports.libDir = path.join(exports.testDir, '../lib');
 exports.tmpDirName = 'tmp';
 // PORT should match the definition in test/testpy/__init__.py.
 exports.PORT = +process.env.NODE_COMMON_PORT || 12346;