No strchrnul() on OpenBSD

Index: libweston/renderer-gl/gl-renderer.c
--- libweston/renderer-gl/gl-renderer.c.orig
+++ libweston/renderer-gl/gl-renderer.c
@@ -4684,7 +4684,9 @@ gl_renderer_log_extensions(struct gl_renderer *gr,
 	l = weston_log_scope_printf(gr->extensions_scope, "%s:", name);
 	p = extensions;
 	while (*p) {
-		end = strchrnul(p, ' ');
+		end = strchr(p, ' ');
+		if (!end)
+			end = p + strlen(p);
 		len = end - p;
 		if (l + len > 78) {
 			l = weston_log_scope_printf(gr->extensions_scope,
