[php-src] PR #23689: Fix GH-20920: fix build with LibreSSL

Pull Request: https://github.com/php/php-src/pull/23689 Author: gvozdetsky Fixes #20920. Supersedes #20932 — thanks to @jordikroon for the original patch and for letting me pick this up. This addresses two of the three LibreSSL build failures reported in GH-20920, one commit each. **1. ENGINE_cleanup() called without a prototype** The call used to be guarded by #ifndef OPENSSL_NO_ENGINE. The v1/v3 backend split in d662ab5f08a moved it from ext/openssl/openssl.c into ext/openssl/openssl_backend_v1.c and kept only the surrounding #ifdef LIBRESSL_VERSION_NUMBER. LibreSSL defines OPENSSL_NO_ENGINE, so <openssl/engine.h> is not included and the call is compiled without a prototype — a warning with older compilers, an error with GCC 14 and later, which default to C23. That is what @bkuhls hit with gcc15. This restores the guard, so the call matches the condition of its include, as suggested by @botovq. **2. PKCS7_NO_DUAL_CONTENT is not always available** The constant was only added in LibreSSL 4.3.0. Following @sthen's suggestion, it is guarded on the macro itself rather than on LIBRESSL_VERSION_NUMBER, so that LibreSSL 4.3.0 and later — which added the macro in response to this very report (openbsd/src@a7d6713) — keep exposing it. ### Testing Built with --enable-debug --enable-zts against LibreSSL 4.2.1 and 4.3.2 (both built from source) and against OpenSSL 3.0.13: * LibreSSL 4.2.1 reproduces both errors on PHP-8.5 and compiles cleanly with this PR. * Under LibreSSL 4.3.2, the set of failing ext/openssl tests is identical with and without this PR (26 pre-existing LibreSSL incompatibilities: removed TLS 1.0/1.1, DH/DSA differences, openssl_error_string() formats, security_level). So this PR neither fixes nor breaks any of them. * Under LibreSSL 4.3.2 the constant is still registered (PKCS7_NO_DUAL_CONTENT === 65536), confirming the macro-based guard. * On OpenSSL 3.0.13: ext/openssl 214 passed, 0 failed, 15 skipped — no behaviour change, since OPENSSL_NO_ENGINE is not defined there and the constant exists. ### This is not sufficient on its own Linking still fails under LibreSSL with: ``` undefined reference to `sk_X509_new_reserve' ext/openssl/openssl_backend_common.c:714 (php_openssl_load_all_certs_from_file) ``` #21430 fixes that, and it is needed on PHP-8.5 as well, not only on master. With #21430 applied on top of this PR, the build against LibreSSL 4.2.1 completes successfully. @bkuhls, @bneumeier — could you confirm this matches what you see on your LibreSSL setups?