phar: exercise CGI branch in gh21797 regression test

Set variables_order=EGPC, register_argc_argv=0 and cgi.fix_pathinfo=0
to keep TRACK_VARS_SERVER IS_UNDEF and route through the pre-4.3 CGI
path, which leaves SCRIPT_NAME unset while still populating
request_uri from PATH_INFO. This reaches the sapi_getenv(SCRIPT_NAME)
-> NULL call that the fix guards against; the prior CLI stub never
entered the CGI/FastCGI branch at all.

Author: iliaal

ext/phar/tests/gh21797.phpt

@@ -1,29 +1,28 @@
 --TEST--
 GH-21797: Phar::webPhar() NULL dereference when SCRIPT_NAME absent from SAPI environment
+--CGI--
 --EXTENSIONS--
 phar
 --INI--
 phar.readonly=0
 phar.require_hash=0
+variables_order=EGPC
+register_argc_argv=0
+cgi.fix_pathinfo=0
+--ENV--
+REQUEST_METHOD=GET
+PATH_INFO=/gh21797.phar
 --FILE--
 <?php
-// The NULL dereference in the CGI/FastCGI branch of webPhar() is not
-// reachable from CLI SAPI. This test exercises the CLI code path as a
-// regression baseline and verifies the function behaves correctly when
-// called outside an HTTP context.
-
 $fname = __DIR__ . '/' . basename(__FILE__, '.php') . '.phar';
-
 $phar = new Phar($fname);
 $phar->addFromString('index.php', '<?php echo "ok\n"; ?>');
 $phar->setStub('<?php
 Phar::webPhar();
+echo "no crash\n";
 __HALT_COMPILER(); ?>');
 unset($phar);
-
-// webPhar() with no HTTP context returns silently (no request method set)
 include $fname;
-echo "no crash\n";
 ?>
 --CLEAN--
 <?php @unlink(__DIR__ . '/' . basename(__FILE__, '.clean.php') . '.phar'); ?>