Only add USB_PRODUCT and USB_MANUFACTURER to flags if defined
Only add USB_PRODUCT and USB_MANUFACTURER to flags if defined

sudar/Arduino-Makefile,marioaugustorama/Arduino-Makefile,WeAreLeka/Arduino-Makefile,WeAreLeka/Arduino-Makefile,marioaugustorama/Arduino-Makefile,sej7278/Arduino-Makefile,tuna-f1sh/Arduino-Makefile,WeAreLeka/Arduino-Makefile,sej7278/Arduino-Makefile,tuna-f1sh/Arduino-Makefile,sudar/Arduino-Makefile