test: make tmpdir.js importable from esm

PR-URL: #44322
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ian Sutherland <ian@iansutherland.ca>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/common/tmpdir.js

@@ -19,8 +19,8 @@ const tmpPath = path.join(testRoot, tmpdirName);
 
 let firstRefresh = true;
 function refresh() {
-  rmSync(this.path);
-  fs.mkdirSync(this.path);
+  rmSync(tmpPath);
+  fs.mkdirSync(tmpPath);
 
   if (firstRefresh) {
     firstRefresh = false;