have a config file?

[WestfW]

I'm all proud of the ability to issue commands like:
make atmega328p AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=0 UART=0
the number of available options is getting large, and it might be nice to use some sort of easily sharable config file as well.
Maybe
make config=<filename.mk>

[WestfW]

config files might even replace makefile changes for vendor boards, ie:
make config=wildfirev3.mk
That way vendors could provide config files instead of needing "me" to edit makefiles.