Keep image zone rules cache separate oracle#2637

* Before this patch,
the image would contain zone rules cache from the JVM computing the image.
* Side effects here,
such as class or source cache lookups,
were affecting its contents and leading to error when writing image.
* With this change,
we guarantee that the zone rules cache in the image is a brand new instance,
separate from the one in the JVM computing the image.

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/Target_java_time_zone_ZoneRules.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2020, 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.svm.core.jdk;
+
+import com.oracle.svm.core.annotate.Alias;
+import com.oracle.svm.core.annotate.RecomputeFieldValue;
+import com.oracle.svm.core.annotate.TargetClass;
+
+import java.time.zone.ZoneOffsetTransition;
+import java.time.zone.ZoneRules;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+@TargetClass(ZoneRules.class)
+final class Target_java_time_zone_ZoneRules {
+
+    @SuppressWarnings("unused") //
+    @Alias @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.NewInstance, declClass = ConcurrentHashMap.class) //
+    private transient ConcurrentMap<Integer, ZoneOffsetTransition[]> lastRulesCache;
+
+}