Add ifunc for variable test-case

Also move ifunc tests to clang and c++.

Test: bionic-unit-tests --gtest_filter=dlfcn.ifunc*
Change-Id: I008c4fc01470c8e4d314003c03a2b63ff9bf7fd8
diff --git a/tests/libs/dlopen_testlib_ifunc_variable.cpp b/tests/libs/dlopen_testlib_ifunc_variable.cpp
new file mode 100644
index 0000000..a1f1ab6
--- /dev/null
+++ b/tests/libs/dlopen_testlib_ifunc_variable.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+extern "C" const char* foo;
+
+extern "C" const char* foo_library() {
+   return foo;
+}