Nice error for global include of binder/Enum.h

Instead of "could not find header", if someone is relying on global
includes and using this new binder/AIDL feature, they will be instructed
how to switch to relying on libbinder headers.

Fixes: 169874616
Test: build only
Change-Id: I67ac5cfdbf088e244ad4f840045e785bf5b14e02
diff --git a/include/binder/Enum.h b/include/binder/Enum.h
new file mode 100644
index 0000000..4c25654
--- /dev/null
+++ b/include/binder/Enum.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#pragma once
+
+#error Do not rely on global include files. All Android cc_* programs are given access to \
+    include_dirs for frameworks/native/include via global configuration, but this is legacy \
+    configuration. Instead, you should have a direct dependency on libbinder OR one of your \
+    dependencies should re-export libbinder headers with export_shared_lib_headers.