File U_build-fix.patch of Package glu

--- glu-9.0.0.orig/src/libutil/error.c	2020-01-05 19:35:08.141802000 +0100
+++ glu-9.0.0/src/libutil/error.c	2020-01-05 19:37:01.707186000 +0100
@@ -30,6 +30,7 @@
 
 #include "gluos.h"
 #include "gluint.h"
+#include <stddef.h>
 #include <GL/glu.h>