net/yate: Disable FORTIFY_SOURCE properly

This reverts commit 4cc2afdcdc which
disabled FORTIFY_SOURCE by removing OpenWrt's CPPFLAGS from the built.
Instead PKG_FORTIFY_SOURCE:=0 is defined, which is the proper way to do
it.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>

net/yate/Makefile

@@ -27,6 +27,9 @@ PKG_FIXUP:=autoreconf
 
 PKG_INSTALL:=1
 
+# Yate currently does not compile with FORTIFY_SOURCE enabled
+PKG_FORTIFY_SOURCE:=0
+
 include $(INCLUDE_DIR)/uclibc++.mk
 include $(INCLUDE_DIR)/package.mk
 
@@ -83,6 +86,9 @@ define Package/$(PKG_NAME)-collection-basic
    TITLE := Basic Yate Server
 endef
 
+# Otherwise yate ignores CPPFLAGS
+TARGET_CFLAGS += $(TARGET_CPPFLAGS)
+
 CONFIGURE_ARGS+= \
 	$(if $(CONFIG_x86_64),--enable-sse2) \
 	--disable-sctp \