Assignment statement should not allow a whitespace in variable's name

[asmundak]

$ cat s.mk
X Y :=a
$ make -f s.mk 
s.mk:1: *** empty variable name.  Stop.
$ ckati -f s.mk 
*** No targets.

(and $(.VARIABLES) value contains X Y in Kati case.

[danw]

This is an artifact of Kati largely targeting Make ~3.81 instead of 4+ (as Android makefiles have never run with Make 4+). On Make 3.81 (in a 14.04 docker image):

# cat s.mk
X Y :=a
$(info X = $(X))
$(info Y = $(Y))
$(info X Y = $(X Y))
# make -f s.mk
X =
Y =
X Y = a
make: *** No targets.  Stop.