engine: remove mention of LibreSSL from OpenSSL::Engine

These paths are only reachable when it is compiled against OpenSSL.
LibreSSL 3.9 does not support ENGINE and defines OPENSSL_NO_ENGINE.

Author: rhenium

ext/openssl/extconf.rb

@@ -123,6 +123,7 @@ def find_openssl_library
   checking_for("LibreSSL version >= 3.9.0") {
     try_static_assert("LIBRESSL_VERSION_NUMBER >= 0x30900000L", "openssl/opensslv.h") }
 else
+  is_openssl = true
   checking_for("OpenSSL version >= 1.0.2") {
     try_static_assert("OPENSSL_VERSION_NUMBER >= 0x10002000L", "openssl/opensslv.h") }
 end
@@ -143,11 +144,13 @@ def find_openssl_library
 
 # compile options
 have_func("RAND_egd()", "openssl/rand.h")
-engines = %w{dynamic 4758cca aep atalla chil
-             cswift nuron sureware ubsec padlock capi gmp gost cryptodev}
-engines.each { |name|
-  have_func("ENGINE_load_#{name}()", "openssl/engine.h")
-}
+if is_openssl
+  engines = %w{dynamic 4758cca aep atalla chil
+               cswift nuron sureware ubsec padlock capi gmp gost cryptodev}
+  engines.each { |name|
+    have_func("ENGINE_load_#{name}()", "openssl/engine.h")
+  }
+end
 
 # added in 1.1.0
 if !have_struct_member("SSL", "ctx", "openssl/ssl.h") || is_libressl

ext/openssl/ossl_engine.c

@@ -47,7 +47,7 @@ static VALUE eEngineError;
 /*
  * Private
  */
-#if !defined(LIBRESSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x10100000
+#if OSSL_OPENSSL_PREREQ(1, 1, 0)
 #define OSSL_ENGINE_LOAD_IF_MATCH(engine_name, x) \
 do{\
   if(!strcmp(#engine_name, RSTRING_PTR(name))){\
@@ -163,7 +163,7 @@ ossl_engine_s_load(int argc, VALUE *argv, VALUE klass)
 static VALUE
 ossl_engine_s_cleanup(VALUE self)
 {
-#if defined(LIBRESSL_VERSION_NUMBER) || OPENSSL_VERSION_NUMBER < 0x10100000
+#if !OSSL_OPENSSL_PREREQ(1, 1, 0)
     ENGINE_cleanup();
 #endif
     return Qnil;