[avr-gcc-list] Makefiles, $(AS) $(ASFLAGS) - simple-minded question

[Dave N6NZ]

I'm working on a new generic Makefile for my projects, and am 
contemplating the most sensible way to define .S handling.

The first thought that popped to mind is:
(lots of unrelated stuff omitted)
AS = avr-as
ASFLAGS = -mmcu=$(MCU)
%o: %.S $(HEADERS)
        $(AS) $(ASFLAGS) -o $@ $<

(All untested code, as of yet, BTW....)

So, I starting wondering... does the avr-gcc driver pick up $(ASFLAGS) 
for .s files, so will my setting of ASFLAGS interact with avr-gcc?

Maybe it makes more sense for me to pick on a non-standard variable name?

Anything else silly about the above rules?

-dave