Make module `core-all-system-modules` visible to art/test subpackages.

This module is used in the definition of `art-run-test-defaults`, used
by ART run-test modules defined under art/test.

Test: n/a
Bug: 147814778
Change-Id: Iaf677783f96196f00d9b9b739b64fabc14cdb9d0
diff --git a/JavaLibrary.bp b/JavaLibrary.bp
index 21fc888..d6e8572 100644
--- a/JavaLibrary.bp
+++ b/JavaLibrary.bp
@@ -207,6 +207,7 @@
     // Visibility is deliberately restricted to a small set of build modules that
     // the core library team control.
     visibility: [
+        "//art/test:__subpackages__",
         "//external/apache-harmony:__subpackages__",
         "//external/apache-xml",
         "//external/okhttp",