bug symfony#31012 [Process] Fix missing $extraDirs when open_basedir returns (arsonik)

This PR was submitted for the master branch but it was merged into the 3.4 branch instead (closes symfony#31012).

Discussion
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[Process] Fix missing $extraDirs when open_basedir returns

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  |no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#31010
| License       | MIT

Fix missing $extraDirs when open_basedir returns

Commits
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e238c89 Fix missing $extraDirs when open_basedir returns

Author: fabpot

src/Symfony/Component/Process/ExecutableFinder.php

@@ -51,7 +51,10 @@ public function addSuffix($suffix)
     public function find($name, $default = null, array $extraDirs = [])
     {
         if (ini_get('open_basedir')) {
-            $searchPath = explode(PATH_SEPARATOR, ini_get('open_basedir'));
+            $searchPath = array_merge(
+                explode(PATH_SEPARATOR, ini_get('open_basedir')),
+                $extraDirs
+            );
             $dirs = [];
             foreach ($searchPath as $path) {
                 // Silencing against https://bugs.php.net/69240