Separate ICU4J from core-libart

- It adds the new core-icu4j into boot classpath

Bug: 138994281
Test: CtsLibcoreTestCases
Change-Id: I6e8d971f304fe9f4836fcd73818720ed83d38154
diff --git a/build/apex/art_apex_test.py b/build/apex/art_apex_test.py
index f670d57..b56b171 100755
--- a/build/apex/art_apex_test.py
+++ b/build/apex/art_apex_test.py
@@ -469,6 +469,7 @@
     # Check java libraries for Managed Core Library.
     self._checker.check_java_library('apache-xml')
     self._checker.check_java_library('bouncycastle')
+    self._checker.check_java_library('core-icu4j')
     self._checker.check_java_library('core-libart')
     self._checker.check_java_library('core-oj')
     self._checker.check_java_library('okhttp')