Allow cross compile of wipe (courtesy Ivan Kuten)

package/wipe/wipe.mk

@@ -33,7 +33,7 @@ $(WIPE_DIR)/.configured: $(WIPE_DIR)/.unpacked
 
 $(WIPE_DIR)/$(WIPE_BINARY): $(WIPE_DIR)/.configured
 	rm -f $(WIPE_DIR)/$(WIPE_BINARY)
-	$(MAKE) CC=$(TARGET_CC) -C $(WIPE_DIR) generic
+	$(MAKE) CC=$(TARGET_CC) CC_GENERIC=$(TARGET_CC) -C $(WIPE_DIR) generic
 
 $(TARGET_DIR)/$(WIPE_TARGET_BINARY): $(WIPE_DIR)/$(WIPE_BINARY)
 	cp -a $(WIPE_DIR)/$(WIPE_BINARY) $(TARGET_DIR)/$(WIPE_TARGET_BINARY)