conf/local.conf.sample: comment out ASSUME_PROVIDED=libsdl-native

Ubuntu 15.10 and Debian testing can't build qemu-native against the host libsdl.
Now that libsdl-native is buildable, comment out the ASSUME_PROVIDED which meant
it wouldn't be used.

[ YOCTO #8553 ]

(From meta-yocto master rev: 759accbfca46de058ce402938713189dab22a70c)

(From meta-yocto rev: aa4ad74c23b283f545a0f9f1ee57635fbe1a1dc6)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Joshua Lock <joshua.g.lock@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-yocto/conf/local.conf.sample

@@ -219,11 +219,12 @@ BB_DISKMON_DIRS = "\
 # Qemu configuration
 #
 # By default qemu will build with a builtin VNC server where graphical output can be
-# seen. The two lines below enable the SDL backend too. This assumes there is a
-# libsdl library available on your build system.
+# seen. The two lines below enable the SDL backend too. By default libsdl-native will
+# be built, if you want to use your host's libSDL instead of the minimal libsdl built
+# by libsdl-native then uncomment the ASSUME_PROVIDED line below.
 PACKAGECONFIG_append_pn-qemu-native = " sdl"
 PACKAGECONFIG_append_pn-nativesdk-qemu = " sdl"
-ASSUME_PROVIDED += "libsdl-native"
+#ASSUME_PROVIDED += "libsdl-native"
 
 
 # CONF_VERSION is increased each time build/conf/ changes incompatibly and is used to