Fix: Build with OpenSSL 3.5+ which removed engine API (#12902)

* Guard engine.h include with HAVE_ENGINE_LOAD_DYNAMIC -- OpenSSL 3.5
  removed the header entirely; only include it when cmake detected the
  ENGINE API is available.
* Fix check_symbol_exists header path from "include/openssl/engine.h"
  to "openssl/engine.h" for consistency with all other OpenSSL checks.

Author: bryancall

CMakeLists.txt

@@ -545,9 +545,9 @@ check_symbol_exists(SSL_get_all_async_fds openssl/ssl.h TS_USE_TLS_ASYNC)
 check_symbol_exists(OSSL_PARAM_construct_end "openssl/params.h" HAVE_OSSL_PARAM_CONSTRUCT_END)
 check_symbol_exists(TLS1_3_VERSION "openssl/ssl.h" TS_USE_TLS13)
 check_symbol_exists(MD5_Init "openssl/md5.h" HAVE_MD5_INIT)
-check_symbol_exists(ENGINE_load_dynamic "include/openssl/engine.h" HAVE_ENGINE_LOAD_DYNAMIC)
-check_symbol_exists(ENGINE_get_default_RSA "include/openssl/engine.h" HAVE_ENGINE_GET_DEFAULT_RSA)
-check_symbol_exists(ENGINE_load_private_key "include/openssl/engine.h" HAVE_ENGINE_LOAD_PRIVATE_KEY)
+check_symbol_exists(ENGINE_load_dynamic "openssl/engine.h" HAVE_ENGINE_LOAD_DYNAMIC)
+check_symbol_exists(ENGINE_get_default_RSA "openssl/engine.h" HAVE_ENGINE_GET_DEFAULT_RSA)
+check_symbol_exists(ENGINE_load_private_key "openssl/engine.h" HAVE_ENGINE_LOAD_PRIVATE_KEY)
 check_symbol_exists(sysctlbyname "sys/sysctl.h" HAVE_SYSCTLBYNAME)
 
 if(SSLLIB_IS_OPENSSL3)

src/iocore/net/SSLUtils.cc

@@ -54,7 +54,9 @@
 #include <openssl/conf.h>
 #include <openssl/dh.h>
 #include <openssl/ec.h>
+#if HAVE_ENGINE_LOAD_DYNAMIC
 #include <openssl/engine.h>
+#endif
 #include <openssl/err.h>
 #include <openssl/evp.h>
 #include <openssl/objects.h>