gnu: vlc: Fix build.

* gnu/packages/patches/vlc-fix-test_libvlc_slaves.patch: New file.
* gnu/local.mk (dist_patch_DATA): Reference new file.
* gnu/packages/video.scm (vlc): Apply patch.

gnu/local.mk

@@ -1412,6 +1412,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/vinagre-newer-freerdp.patch             \
   %D%/packages/patches/vinagre-newer-rdp-parameters.patch      \
   %D%/packages/patches/virglrenderer-CVE-2017-6386.patch 	\
+  %D%/packages/patches/vlc-fix-test_libvlc_slaves.patch \
   %D%/packages/patches/vorbis-tools-CVE-2014-9638+CVE-2014-9639.patch		\
   %D%/packages/patches/vorbis-tools-CVE-2014-9640.patch		\
   %D%/packages/patches/vorbis-tools-CVE-2015-6749.patch		\

gnu/packages/patches/vlc-fix-test_libvlc_slaves.patch

@@ -0,0 +1,35 @@
+From 4186c94104ee528abd6860611b49515f3e6ec644 Mon Sep 17 00:00:00 2001
+From: Thomas Guillem <thomas@gllm.fr>
+Date: Fri, 18 Oct 2019 10:34:07 +0200
+Subject: [PATCH] input/item: sort before attaching slaves
+
+The order of readdir() is completely filesystem dependent.
+
+Slaves should be attached using the same order across multiple OSses/access
+modules.
+
+This fixes the test_libvlc_slaves on some system when the entry order from
+readdir() is different.
+
+This patch need to be backported to VLC 3.0.
+---
+ src/input/item.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/input/item.c b/src/input/item.c
+index e8db39ca28..fbd74cc95f 100644
+--- a/src/input/item.c
++++ b/src/input/item.c
+@@ -1809,8 +1809,8 @@ void vlc_readdir_helper_finish(struct vlc_readdir_helper *p_rdh, bool b_success)
+ {
+     if (b_success)
+     {
+-        rdh_attach_slaves(p_rdh, p_rdh->p_node);
+         rdh_sort(p_rdh->p_node);
++        rdh_attach_slaves(p_rdh, p_rdh->p_node);
+     }
+     free(p_rdh->psz_ignored_exts);
+ 
+-- 
+2.20.1
+

gnu/packages/video.scm

@@ -1095,7 +1095,13 @@ videoformats depend on the configuration flags of ffmpeg.")
                     "/vlc-" version ".tar.xz"))
               (sha256
                (base32
-               "1xmxjpyzdhabchwncz6lvx3kzvl7fz9c42bkv3nbj68albs9w570"))))
+                "1xmxjpyzdhabchwncz6lvx3kzvl7fz9c42bkv3nbj68albs9w570"))
+              (patches
+               (search-patches
+                ;; TODO: The test "libvlc_slaves" fails.  Applied upstream as
+                ;; <https://git.videolan.org/?p=vlc.git;a=commit;h=4186c94104ee528abd6860611b49515f3e6ec644>.
+                ;; Try removing it in 3.0.9.
+                "vlc-fix-test_libvlc_slaves.patch"))))
     (build-system gnu-build-system)
     (native-inputs
      `(("flex" ,flex)