minor #58747 [Process] fix the directory separator being used (xabbuh)

This PR was merged into the 5.4 branch.

Discussion
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[Process] fix the directory separator being used

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        |
| License       | MIT

Commits
-------

2526495eb75 fix the directory separator being used

Author: nicolas-grekas

Diff for: Tests/ExecutableFinderTest.php

@@ -148,7 +148,7 @@ public function testFindBatchExecutableOnWindows()
      */
     public function testEmptyDirInPath()
     {
-        putenv(sprintf('PATH=%s:', \dirname(\PHP_BINARY)));
+        putenv(sprintf('PATH=%s%s', \dirname(\PHP_BINARY), \PATH_SEPARATOR));
 
         try {
             touch('executable');