iptables: fix rebuild errors on configuration changes

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 48314

package/network/utils/iptables/Makefile

@@ -448,6 +448,20 @@ MAKE_FLAGS := \
 	KBUILD_OUTPUT="$(LINUX_DIR)" \
 	BUILTIN_MODULES="$(patsubst ip6t_%,%,$(patsubst ipt_%,%,$(patsubst xt_%,%,$(IPT_BUILTIN) $(IPT_CONNTRACK-m) $(IPT_NAT-m))))"
 
+ifneq ($(wildcard $(PKG_BUILD_DIR)/.config_*),$(subst .configured_,.config_,$(STAMP_CONFIGURED)))
+  define Build/Configure/rebuild
+	$(FIND) $(PKG_BUILD_DIR) -name \*.o -or -name \*.\?o -or -name \*.a | $(XARGS) rm -f
+	rm -f $(PKG_BUILD_DIR)/.config_*
+	rm -f $(PKG_BUILD_DIR)/.configured_*
+	touch $(subst .configured_,.config_,$(STAMP_CONFIGURED))
+  endef
+endif
+
+define Build/Configure
+$(Build/Configure/rebuild)
+$(Build/Configure/Default)
+endef
+
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include
 	$(INSTALL_DIR) $(1)/usr/include/iptables