[FrameworkBundle] Fix server start in case the PHP binary is not found
bug #12490 [2.6][FrameworkBundle] Fix server start in case the PHP binary is not found (romainneutron)

This PR was merged into the 2.6 branch.

Discussion
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[2.6][FrameworkBundle] Fix server start in case the PHP binary is not found

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

Commits
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a6b1cfc [FrameworkBundle] Fix server start in case the PHP binary is not found