bug symfony#14841 [DoctrineBridge] Fixed symfony#14840 (saksmt)

This PR was squashed before being merged into the 2.3 branch (closes symfony#14841).

Discussion
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[DoctrineBridge] Fixed symfony#14840

[DoctrineBridge] Fixed compatibility with entities packed in Phar

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#14840
| License       | MIT
| Doc PR        | none

Commits
-------

92ad5df [DoctrineBridge] Fixed symfony#14840

Author: fabpot

src/Symfony/Bridge/Doctrine/DependencyInjection/AbstractDoctrineExtension.php

@@ -129,11 +129,15 @@ protected function setMappingDriverAlias($mappingConfig, $mappingName)
      */
     protected function setMappingDriverConfig(array $mappingConfig, $mappingName)
     {
-        if (!is_dir($mappingConfig['dir'])) {
+        $mappingDirectory = $mappingConfig['dir'];
+        if (!is_dir($mappingDirectory)) {
             throw new \InvalidArgumentException(sprintf('Invalid Doctrine mapping path given. Cannot load Doctrine mapping/bundle named "%s".', $mappingName));
         }
 
-        $this->drivers[$mappingConfig['type']][$mappingConfig['prefix']] = realpath($mappingConfig['dir']);
+        if (substr($mappingDirectory, 0, 7) !== 'phar://') {
+            $mappingDirectory = realpath($mappingDirectory);
+        }
+        $this->drivers[$mappingConfig['type']][$mappingConfig['prefix']] = $mappingDirectory;
     }
 
     /**