bug symfony#15603 [HttpKernel] Do not normalize the kernel root directory path symfony#15567 (leofeyer)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes symfony#15603).

Discussion
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[HttpKernel] Do not normalize the kernel root directory path symfony#15567

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#15474
| License       | MIT
| Doc PR        | -

Commits
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a53489e Do not normalize the kernel root directory path (see symfony#15474).

Author: fabpot

src/Symfony/Component/HttpKernel/Kernel.php

@@ -344,7 +344,7 @@ public function getRootDir()
     {
         if (null === $this->rootDir) {
             $r = new \ReflectionObject($this);
-            $this->rootDir = str_replace('\\', '/', dirname($r->getFileName()));
+            $this->rootDir = dirname($r->getFileName());
         }
 
         return $this->rootDir;