subsys/usb/Makefile - third_party/github/zephyrproject-rtos/zephyr - Git at Google

 ccflags-y += -I${srctree}/include/drivers/usb -I${srctree}/usb/include

 obj-$(CONFIG_USB_DEVICE_STACK) += usb_device.o
 obj-$(CONFIG_USB_DEVICE_STACK) += class/
	ccflags-y += -I${srctree}/include/drivers/usb -I${srctree}/usb/include

	obj-$(CONFIG_USB_DEVICE_STACK) += usb_device.o
	obj-$(CONFIG_USB_DEVICE_STACK) += class/