Hi,
it's possible to add some custom php functions to ./build secure_php command?
for example, I want it to include phpinfo, dl, putenv, chmod, ini_set functions in disable_funcion
You can always edit corresponding php.ini and adjust a list of disabled function there. Or simply create your own file (with your own instructions):
/usr/local/php5*/lib/php.conf.d/99-custom.ini
where 5* should replaced by 53, 54, 55, 56, 57 depending on what version of PHP you have. And restart apache/nginx or php-fpm, depending on how you run PHP.