Make __dirname declaration cross-platform

See nodejs/node#37845

Author: aral

lib/staging/monkeyPatchTls.js

@@ -10,8 +10,9 @@
 import fs from 'fs'
 import tls from 'tls'
 import path from 'path'
+import { fileURLToPath } from 'url'
 
-const __dirname = new URL('.', import.meta.url).pathname
+const __dirname = fileURLToPath(new URL('.', import.meta.url))
 
 /**
  * Monkey patches the TLS module to accept the Let’s Encrypt staging certificate.