Add missing file.

sql/wsrep_mysqld_c.h

+/* Copyright 2018-2018 Codership Oy <http://www.codership.com>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+#ifndef WSREP_MYSQLD_C_H
+#define WSREP_MYSQLD_C_H
+
+enum enum_wsrep_certification_rules {
+    WSREP_CERTIFICATION_RULES_STRICT,
+    WSREP_CERTIFICATION_RULES_OPTIMIZED
+};
+
+extern ulong wsrep_certification_rules;
+
+#endif /* WSREP_MYSQLD_C_H */