Fix Solaris tests and add nightly CI job

Closes GH-20709

ext/zlib/tests/zlib_wrapper_flock_basic.phpt

@@ -1,5 +1,11 @@
 --TEST--
 Test function flock on a zlib stream
+--SKIPIF--
+<?php
+if (PHP_OS_FAMILY === 'Solaris') {
+    die('skip Solaris: fcntl-based flock requires write access for LOCK_EX with read-only zlib stream');
+}
+?>
 --EXTENSIONS--
 zlib
 --FILE--