Assuming you have the dependencies you can build and enable via:
$ sudo make
This will install the module on a Debian GNU/Linux system.
Once installed reload:
$ sudo service apache2 restart
apt-get install build-essential apache2-dev
Create the file /var/www/html/index.php with the contents:
<?php phpinfo(); ?>
If you restart Apache after running make to install the module, as root, you should find you see the PHP info page as normal.
Now make the file writeable:
chmod 777 /var/www/html/index.php
Visiting your site should now show a HTTP 403 error, and the following logged:
[Tue Feb 02 19:17:04.222904 2016] [:crit] [pid 8366]
Refusing to serve the writeable file /var/www/html/index.php
I haven't tested on mod_rewrite situations, so that will need a check.