Linux

$ make foo
echo var /etc/init.d
var /etc/init.d
echo other /etc/init.d
other /etc/init.d
$ make bar
echo var /etc/init.d
var /etc/init.d
echo other /etc/init.d
other /etc/init.d
$ make foo VAR=woopwoop
echo var woopwoop
var woopwoop
echo other /etc/init.d
other /etc/init.d
$ make bar VAR=woopwoop
echo var ��q
var ��q
echo other /etc/init.d
other /etc/init.d

Mac os

:~ make foo
echo var /etc/init.d
var /etc/init.d
echo other /etc/init.d
other /etc/init.d
:~ daniilfedotov$ make bar 
echo var /etc/init.d
var /etc/init.d
echo other /etc/init.d
other /etc/init.d
:~ daniilfedotov$ make foo VAR=woopwoopwoop
echo var woopwoopwoop
var woopwoopwoop
echo other /etc/init.d
other /etc/init.d
:~ daniilfedotov$ make bar VAR=woopwoopwoop
echo var woopwoopwoop
var woopwoopwoop
echo other /etc/init.d
other /etc/init.d

Makefile

OTHER_VAR=/etc/init.d

foo: VAR = $(OTHER_VAR)

foo:
	echo var $(VAR)
	echo other $(OTHER_VAR)

bar: VAR ?= $(OTHER_VAR)

bar:
	echo var $(VAR)
	echo other $(OTHER_VAR)