Is there any possibility to use the same Makefile in CentOS and FreeBSD?

Question

Unfortunately, in some old FreeBSD environments I can't use "gmake", so I need to write a Makefile which will work with FreeBSD make also. And the last problem I can't solve - use shell commands, for example, I need to get full path to Python executable:

PYTHON       := $(shell which python2.7 || which python)

But FreeBSD make simply ignores this.

test:
     echo == $(PYTHON) ==

Then I run make test:

$ make test
echo ==  ==
== ==

Can anyone help, please?

Update #1: To those who can't read closely and accidentally downvotes the question:

Whole test script:

PYTHON       != which python2.7 || which python

test:
        $(PYTHON) -c 'print "hello world"'

Run on FreeBSD:

make
/usr/bin/python -c 'print "hello world"'
hello world

Run on CentOS:

make                                 
test_make:1: *** missing separator.  Stop.

And if I use command $(shell ...) it works on CentOS and doesn't work on FreeBSD. So, is there any solution without gmake?

Update #2: Eventually I found solution (put command in backticks):

PYTHON       ?= `which python2.7 || which python`

I don't know why it prints itself:

make
`which python2.7 || which python` -c 'print "hello world"'
hello world

But it works! You can use it, guys :)

Answer 1

You may be able to do:

PYTHON != which python2.7 || which python

This works in gnu make 4.1 and bmake 20160220-2+b1

But why bother? It's honestly probably less trouble to install gnu make and use it, or to write a configure script that generates the Makefile for you with PYTHON properly defined.