ossl.c: do not set locking callbacks on LibreSSL

Similarly to OpenSSL >= 1.1.0, LibreSSL 2.9.0 ensures thread safety
without requiring applications to set locking callbacks and made
related functions no-op.

Author: rhenium

ext/openssl/extconf.rb

@@ -130,7 +130,6 @@ def find_openssl_library
 if !have_struct_member("SSL", "ctx", "openssl/ssl.h") || is_libressl
   $defs.push("-DHAVE_OPAQUE_OPENSSL")
 end
-have_func("CRYPTO_lock") || $defs.push("-DHAVE_OPENSSL_110_THREADING_API")
 have_func("BN_GENCB_new")
 have_func("BN_GENCB_free")
 have_func("BN_GENCB_get_arg")

ext/openssl/ossl.c

@@ -9,7 +9,13 @@
  */
 #include "ossl.h"
 #include <stdarg.h> /* for ossl_raise */
-#include <ruby/thread_native.h> /* for OpenSSL < 1.1.0 locks */
+
+/* OpenSSL >= 1.1.0 and LibreSSL >= 2.9.0 */
+#if defined(LIBRESSL_VERSION_NUMBER) || OPENSSL_VERSION_NUMBER >= 0x10100000
+# define HAVE_OPENSSL_110_THREADING_API
+#else
+# include <ruby/thread_native.h>
+#endif
 
 /*
  * Data Conversion