binutils: enable poison system directories option

This commit enables the poison system directories option, which is now
available thanks to the binutils patches that have been added.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: Romain Naour <romain.naour@openwide.fr>
Tested-by: Romain Naour <romain.naour@openwide.fr>

package/binutils/binutils.mk

@@ -68,6 +68,7 @@ HOST_BINUTILS_CONF_OPTS = --disable-multilib --disable-werror \
 			--target=$(GNU_TARGET_NAME) \
 			--disable-shared --enable-static \
 			--with-sysroot=$(STAGING_DIR) \
+			--enable-poison-system-directories \
 			$(BINUTILS_DISABLE_GDB_CONF_OPTS) \
 			$(BINUTILS_EXTRA_CONFIG_OPTIONS)