Conditional variable define in Makefile with ifeq

I am trying to define variables in a Makefile, according to conditions. As ifeq can be run only in rules, I have added an additional rule (def_rule) I refer to for each rule.

Example:

def_rule:
ifeq ($(TARGET), android)
    CC=arm-linux-androideabi-gcc
else
    echo "native build" 
endf

all:    def_rule tp xi_eid_chipset.o

Unfortunately, invoking make all returns this:

ifeq (linux, android)
/bin/sh: Syntax error: word unexpected (expecting ")")
make: *** [def_rule] Error 2

I cannot figure out why. I have just followed examples in GNU Make documentation.

Do you know how to do conditional defines in Makefiles ?