Backport patch to fix compilation

Resolves: https://issues.redhat.com/browse/RHEL-2982

0001-libutil-Include-stddef.h-for-NULL.patch

@@ -0,0 +1,27 @@
+From b293e7e843cff28c4b925fb0db988395c040d0ef Mon Sep 17 00:00:00 2001
+From: Matt Turner <mattst88@gmail.com>
+Date: Tue, 23 Jul 2019 10:42:41 -0700
+Subject: [PATCH] libutil: Include stddef.h for NULL
+
+Fixes: #5
+
+Reviewed-by: Eric Engestrom <eric@engestrom.ch>
+---
+ src/libutil/error.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/src/libutil/error.c b/src/libutil/error.c
+index 7212748..d3b2666 100644
+--- a/src/libutil/error.c
++++ b/src/libutil/error.c
+@@ -30,6 +30,7 @@
+ 
+ #include "gluos.h"
+ #include "gluint.h"
++#include <stddef.h>
+ #include <GL/glu.h>
+ 
+ 
+-- 
+2.45.2
+

mesa-libGLU.spec

@@ -12,6 +12,7 @@ Source2:        make-git-snapshot.sh
 
 Patch1: 0001-glu-initialize-PriorityQ-order-field-to-NULL-in-pqNe.patch
 Patch2: 0002-Add-D-N-DEBUG-to-CFLAGS-dependent-on-enable-debug.patch
+Patch3: 0001-libutil-Include-stddef.h-for-NULL.patch
 
 BuildRequires:  autoconf automake libtool
 BuildRequires:  mesa-libGL-devel
@@ -35,6 +36,7 @@ developing applications that use %{name}.
 %setup -q -n glu-%{?gitdate:%{gitdate}}%{?!gitdate:%{version}}
 %patch1 -p1
 %patch2 -p1
+%patch3 -p1
 
 %build
 autoreconf -v -i -f