MDEV-5120 Test suite test maria-no-logging fails

stat structure (from <sys/stat.h>) is conditionally defined
to have different layout and size depending on the defined macros.
The correct macro is defined in my_config.h, which means it MUST be
included first (or, at least before <features.h> - so, practically,
before including any system headers).

plugin/server_audit/server_audit.c

@@ -17,6 +17,8 @@
 #define PLUGIN_VERSION 0x101
 #define PLUGIN_STR_VERSION "1.1.7"
 
+#include <my_config.h>
+
 #include <stdio.h>
 #include <time.h>
 #include <string.h>