Description:
------------
This issue affects both 7.0.19 and 7.1.5, and is new to both of those versions as far as I can tell. On a system with PaX enabled, I get the following build error:

  Generating phar.php
  Generating phar.phar
  PEAR package PHP_Archive not installed: generated phar will require PHP's 
  phar extension be enabled.
  make: *** [Makefile:359: ext/phar/phar.phar] Killed

Notice the "Killed" there at the end. That comes from the "php" CLI binary, as dmesg shows:

  [Thu May 11 20:59:17 2017] PAX: execution attempt in: <anonymous mapping>, 
  38cf40bc000-38cf40cc000 38cf40bc000

  [Thu May 11 20:59:17 2017] PAX: terminating task: /var/tmp/portage/dev-lang
  /php-7.1.5/work/sapis-build/cli/sapi/cli/php(php):7930, uid/euid: 250/250, 
  PC: 0000038cf40bc010, SP: 000003fa7ab2a118

I'm not sure that this is a PHP bug, but it's new in v7.0.19 and v7.1.5, so it's suspicious. To reproduce it, all one has to do is try to build PHP on a hardened Gentoo system (which are fairly common).

As a workaround, we could pax-mark the "php" binary, but that nullifies a strong security measure.