Short version

Why does this unmodified code from the official PHP 5.6.18 release:

--SKIPIF--
<?php
if (phpversion() < "5.3.0") { die('SKIP php version so lower.'); }
if (!extension_loaded('openssl')) { die('ext/openssl required'); }
if(substr(PHP_OS, 0, 3) != 'WIN' ) {
        die('skip windows only test');
}
?>

... not cause a windows-only test to be skipped when I'm building the PHP package on Arch Linux?

Long version

I'm trying to build PHP5.6.18 using the PKGBUILD from the official Arch Build System. Here's what I've done:

1. git clone git://projects.archlinux.org/svntogit/packages.git
2. I went through the git history of the php package, and identified this commit as the best starting point - basically the last commit before the uprev to PHP7. So, I cd into packages, and git checkout that commit ID.
3. I updated the PKGBUILD like this:
   • set pkgver=5.6.18
   • set pkgrel=1
   • set the first md5sum to '177ba962557795866ae331ad4ad99bba'
4. setup clean chroot for building (this reduced the test failures from 2-3 to 1)
5. Build php: makechrootpkg -c -r $CHROOT (in the directory with the PKGBUILD file.

The build works fine, but I get the following test failure:

Number of tests : 6651              6180
Tests skipped   :  471 (  7.1%) --------
Tests warned    :    1 (  0.0%) (  0.0%)
Tests failed    :    1 (  0.0%) (  0.0%)
Expected fail   :    9 (  0.1%) (  0.1%)
Tests passed    : 6169 ( 92.8%) ( 99.8%)
---------------------------------------------------------------------
Time taken      :   45 seconds
...
FAILED TEST SUMMARY
---------------------------------------------------------------------
mixed stream_socket_enable_crypto(resource $stream , bool $enable [, int $crypto_type [, resource $session_stream
]] ) ; [ext/standard/tests/streams/stream_socket_enable_crypto-win32.phpt]
=====================================================================

=====================================================================
WARNED TEST SUMMARY
---------------------------------------------------------------------
Bug #70172 - Use After Free Vulnerability in unserialize() [ext/standard/tests/serialize/bug70172.phpt] (warn: XFA
IL section but test passes)
=====================================================================

OK, so the win32 already looks suspicious in the filename, and a look at the file contents indeed suggests that the test should be skipped on Linux:

--TEST--
mixed stream_socket_enable_crypto(resource $stream , bool $enable [, int $crypto_type [, resource $session_stream ]] ) ;
...
--SKIPIF--
<?php
if (phpversion() < "5.3.0") { die('SKIP php version so lower.'); }
if (!extension_loaded('openssl')) { die('ext/openssl required'); }
if(substr(PHP_OS, 0, 3) != 'WIN' ) {
        die('skip windows only test');
}
?>

Note the PHP_OS related check. So, I'm thinking, maybe PHP_OS is somehow getting the wrong value. So, I:

1. Manually go into the build chroot: arch-nspawn $CHROOT/$USER/
2. Add echo substr(PHP_OS, 0, 3) to the beginning of that test (just under the <?php in the --FILE-- section, and in the actual stream_socket_enable_crypto-win32.php file)
3. Re-run it using the stream_socket_enable_crypto-win32.sh script in the same directory, I indeed see the expected Lin output.

Why is this test not skipped? I'm really confused. How can I fix this issue?