include libgen.h for basename(3)

Index: tests/util/piglit-framework-gl.c
--- tests/util/piglit-framework-gl.c.orig
+++ tests/util/piglit-framework-gl.c
@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#include <libgen.h>
 
 #include "piglit-util-gl.h"
 #include "piglit-framework-gl/piglit_gl_framework.h"