I do well see the drivers inside...
media_build/linux/drivers/media/usb/dvb-usb-v2/it913x.c and media_build/linux/drivers/media/dvb-frontends/it913x-fe*
as well in the build output: media_build/v4l/dvb-usb-it913x.ko and media_build/v4l/it913x-fe.ko
so they will definitly compile, are you sure, the build succeeded without any error? The firmware must be extracted separately. The build doensn't provide it.