Fix GH-14590: Memory leak in FPM test gh13563-conf-bool-env.phpt

[nielsdos]

The issue is not related to FPM. Values retrieved from zend_getenv should be freed.
Making a test is not trivial because the CLI sapi doesn't implement the sapi getenv hook, so zend_getenv always returns NULL.

[devnexen]

Quick (genuine) question, if it depends on the actual sapi, do all callbacks use zend alloc api consistently for every case (and platforms) ?

[nielsdos]

The only possible value for zend_getenv is sapi_getenv which uses zend alloc to duplicate the string that it reads from the SAPI module.

[devnexen]

Makes sense thx.

[jorgsowa]

Thank you for fixing it! Why can't you take a minimal test case from the bug report? Example without correct OUTPUT: master...jorgsowa:php-src:bug-gh-14590-test-case

[nielsdos]

@jorgsowa I suppose we can, I didn't do it because it would tie the test to fpm although the issue is not related to fpm at all. Feel free to submit that as a PR.