Exclude Symfony polyfills from php-scoper isolation.

See humbug/php-scoper#440

scoper.inc.php

@@ -9,9 +9,17 @@
  * file that was distributed with this source code.
  */
 
+use Isolated\Symfony\Component\Finder\Finder;
+
+$polyfillsBootstrap = Finder::create()
+    ->files()
+    ->in(__DIR__ . '/vendor/symfony/polyfill-*')
+    ->name('bootstrap.php');
+
 return [
     'whitelist' => [
         'Psy\*',
+        'Symfony\Polyfill\*',
 
         // Old Hoa global functions
         'from',
@@ -21,6 +29,13 @@
         'curry_ref',
     ],
 
+    'files-whitelist' => \array_map(
+         static function ($file) {
+             return $file->getPathName();
+         },
+         \iterator_to_array($polyfillsBootstrap)
+     ),
+
     'patchers' => [
         // Un-patch overly enthusiastic internal constant patching.
         // https://github.com/humbug/php-scoper/issues/356