sstrip: mark as deprecated

sstrip is unmaintained and potentially harmful, as Yann explained in
commit 6a6962fd82ca ("build/sstrip: deprecate for 2014.05").

Signed-off-by: Julien Floret <julien.floret@6wind.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/sstrip/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_SSTRIP
 	bool "sstrip"
+	depends on BR2_DEPRECATED_SINCE_2016_08
 	help
 	  Small utility that removes a few bytes from an executable that
 	  strip leaves behind.