conditional macro definitions

[bill]

The syntax
foo:=CFLAGS=-DFOO
for redefining CFLAGS for the target foo seems like a great thing, but 
it's not valid in gnu-make.  I'm currently setting up my make files so 
that I type "make DEBUG=1" and then defining CFLAGS conditionally based 
on the definition of DEBUG.  I'd much rather type "make debug" and use 
the syntax given above.  2 questions:

1)  Is it possible to do something like:
if target==debug;    CFLAGS = -DDEBUG; end if
rather than:
ifdef DEBUG; CFLAGS = -DDEBUG; end if

2) Why is the conditional macro definition syntax not incorporated into 
gnu-make?
It seems like a good idea.