fstools: backport changes to fix build error

Backport: "fstoools: add define for GLOB_ONLYDIR"
Fixes: #478

package/system/fstools/patches/0020-add-define-for-GLOB_ONLYDIR.patch

@@ -0,0 +1,32 @@
+From 5345343828df944ae247d91cc77182f87559bc9a Mon Sep 17 00:00:00 2001
+From: Rosen Penev <rosenp@gmail.com>
+Date: Wed, 25 Mar 2020 16:27:47 -0700
+Subject: [PATCH] fstoools: add define for GLOB_ONLYDIR
+
+This was originally a patch for musl. It is not present in musl as it is a
+GNU extension.
+
+Place it here where it belongs.
+
+Signed-off-by: Rosen Penev <rosenp@gmail.com>
+---
+ libfstools/overlay.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/libfstools/overlay.c b/libfstools/overlay.c
+index 14214a3..39215d5 100644
+--- a/libfstools/overlay.c
++++ b/libfstools/overlay.c
+@@ -30,6 +30,10 @@
+ #include "libfstools.h"
+ #include "volume.h"
+ 
++#ifndef GLOB_ONLYDIR
++#define GLOB_ONLYDIR 0x100
++#endif
++
+ #define SWITCH_JFFS2 "/tmp/.switch_jffs2"
+ 
+ static bool keep_sysupgrade;
+-- 
+2.20.1