toolchain: Include hardening.mk for toolchain build

This adds the hardening options also to the toolchain build.
With this change the /usr/lib/libstdc++.so.6.0.24 library will have
stack canaries and the /lib/libgcc_s.so.1 library will have Full RELRO.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

include/toolchain-build.mk

@@ -12,6 +12,7 @@ HOST_BUILD_PREFIX:=$(TOOLCHAIN_DIR)
 BUILD_DIR_HOST:=$(BUILD_DIR_TOOLCHAIN)
 
 include $(INCLUDE_DIR)/host-build.mk
+include $(INCLUDE_DIR)/hardening.mk
 
 HOST_STAMP_PREPARED=$(HOST_BUILD_DIR)/.prepared