The check to enable/disable this new feature of PHP 7.2 works
incorrectly when cross-compiling because it detects the host headers
only and there is no way to pass in a dedicated directory.

The wish to change this was reported upstream at:
https://bugs.php.net/bug.php?id=75722

For the meantime, use a self-cooked patch.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>