Move platform-private symbols out of libdl.so

Symbols not intended to be accessible from apps are moved to libdl_android.so

Test: bionic-unit-tests
Change-Id: Ib8ba6147a20cf56550c9a008f66570a2d419565a
diff --git a/tests/Android.bp b/tests/Android.bp
index c200ef4..894a7cb 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -467,6 +467,7 @@
             shared_libs: [
                 "ld-android",
                 "libdl",
+                "libdl_android",
                 "libdl_preempt_test_1",
                 "libdl_preempt_test_2",
                 "libdl_test_df_1_global",