package/gstreamer/gst-ffmpeg: needs gcc >= 5.x on SuperH

Compilation triggers an ICE in gcc with gcc <= 4.9 using this defconfig

BR2_sh=y
BR2_TOOLCHAIN_BUILDROOT_WCHAR=y
BR2_PACKAGE_GSTREAMER=y
BR2_PACKAGE_GST_FFMPEG=y
BR2_PACKAGE_GST_FFMPEG_GPL=y

The problem is known upstream, a fix was never committed to gcc <= 4.9:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65151

Compiling gst-ffmpeg with gcc5 works fine using this defconfig:

BR2_sh=y
BR2_TOOLCHAIN_BUILDROOT_WCHAR=y
BR2_GCC_VERSION_5_X=y
BR2_PACKAGE_GSTREAMER=y
BR2_PACKAGE_GST_FFMPEG=y
BR2_PACKAGE_GST_FFMPEG_GPL=y

This patch adds a dependency to gcc >= 5.x to fix the problem as
suggested by Thomas:
http://lists.busybox.net/pipermail/buildroot/2016-February/152584.html

Fixes
http://autobuild.buildroot.net/results/939/939da0c7771ddd97c05cedc0a7afc0ad34a21312/

[Peter: fix ML link, simplify kconfig, add comment explaining why]
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gstreamer/gst-ffmpeg/Config.in

@@ -3,6 +3,8 @@ config BR2_PACKAGE_GST_FFMPEG
 	# Unsupported for MIPS R6. It bundles a version of libav which
 	# doesn't have support for MIPS R6.
 	depends on !BR2_mips_32r6 && !BR2_mips_64r6
+	# triggers https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65151 on sh
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_5 || !BR2_sh
 	select BR2_PACKAGE_GST_PLUGINS_BASE
 	help
 	  GStreamer plugin containing one plugin with a set of elements using
@@ -23,3 +25,6 @@ config BR2_PACKAGE_GST_FFMPEG_GPL
 	  be under GPL.
 
 endif
+
+comment "gst-ffmpeg needs a toolchain w/ gcc >= 5"
+	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_5 && BR2_sh