get_executable_path slight change to make it work under OpenBSD

drivers/unix/os_unix.cpp

@@ -50,7 +50,7 @@
 #include <mach-o/dyld.h>
 #endif
 
-#ifdef __FreeBSD__
+#if defined(__FreeBSD__) || defined(__OpenBSD__)
 #include <sys/param.h>
 #endif
 #include "global_config.h"
@@ -532,7 +532,7 @@ String OS_Unix::get_executable_path() const {
 		return OS::get_executable_path();
 	}
 	return b;
-#elif defined(__FreeBSD__)
+#elif defined(__FreeBSD__) || defined(__OpenBSD__)
 	char resolved_path[MAXPATHLEN];
 
 	realpath(OS::get_executable_path().utf8().get_data(), resolved_path);