gstreamer1.0: add a patch to further fix up the documentation generation

Gstreamer would attempt to launch gst-plugin-scanner binary installed on the host
if the target binary was failing (and it does, intentionally, fail in our case). Most
of the time the host binary is absent, and so this has no effect, but sometimes
it's present, and so the whole thing (running under qemu) fails.

(From OE-Core rev: 8485438140ce6a8d547137c81961125d4296cd6b)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-multimedia/gstreamer/files/0001-gst-gstpluginloader.c-when-env-var-is-set-do-not-fal.patch

@@ -0,0 +1,35 @@
+From a1d7c582392c8bc87fa9411af77b20e011944357 Mon Sep 17 00:00:00 2001
+From: Alexander Kanavin <alex.kanavin@gmail.com>
+Date: Thu, 25 Jan 2018 17:55:02 +0200
+Subject: [PATCH] gst/gstpluginloader.c: when env var is set do not fall
+ through to system plugin scanner
+
+If we set a custom GST_PLUGIN_SCANNER env var, then we probably want to use that and only that.
+
+Falling through to the one installed on the system is problamatic in cross-compilation
+environemnts, regardless of whether one pointed to by the env var succeeded or failed.
+
+Upstream-Status: Pending
+Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
+---
+ gst/gstpluginloader.c | 4 +---
+ 1 file changed, 1 insertion(+), 3 deletions(-)
+
+diff --git a/gst/gstpluginloader.c b/gst/gstpluginloader.c
+index 430829d..3a75731 100644
+--- a/gst/gstpluginloader.c
++++ b/gst/gstpluginloader.c
+@@ -471,9 +471,7 @@ gst_plugin_loader_spawn (GstPluginLoader * loader)
+     helper_bin = g_strdup (env);
+     res = gst_plugin_loader_try_helper (loader, helper_bin);
+     g_free (helper_bin);
+-  }
+-
+-  if (!res) {
++  } else {
+     GST_LOG ("Trying installed plugin scanner");
+ 
+ #ifdef G_OS_WIN32
+-- 
+2.15.1
+

meta/recipes-multimedia/gstreamer/gstreamer1.0.inc

@@ -17,6 +17,7 @@ acpaths = "-I ${S}/common/m4 -I ${S}/m4"
 SRC_URI_append = " \
     file://0001-introspection.m4-prefix-pkgconfig-paths-with-PKG_CON.patch \
     file://gtk-doc-tweaks.patch \
+    file://0001-gst-gstpluginloader.c-when-env-var-is-set-do-not-fal.patch \
 "
 
 PACKAGECONFIG ??= ""