Fix test for Windows ZTS builds

cmb69 · cmb69 · commit bc529b92ee69 · 2020-01-11T06:15:32.000+14:00
Cf. <https://bugs.php.net/bug.php?id=61685#1578672905>.
diff --git a/ext/calendar/tests/easter_date.phpt b/ext/calendar/tests/easter_date.phpt
@@ -2,6 +2,8 @@
 easter_date()
 --INI--
 date.timezone=UTC
+--ENV--
+TZ=UTC
 --SKIPIF--
 <?php include 'skipif.inc'; ?>
 --FILE--
