Build Support for CTS Native Tests

Bug 4970300

Adds two new variables, CTS_TEST_CASES and CTS_TEST_XMLS, to be read
from CtsTestCaseList.mk. The CTS_TEST_CASES variable can be used to
copy any sort of file to the repository/testcases CTS directory.
The CTS_TEST_XMLS variable can be used to inject test package xmls
from any source rather than relying upon the monolithic and
mostly serial buildCts.py script.

The existing CTS_CORE_CASE_LIST is coded to only support APKs, so
it could not be retrofitted to support native tests. However, the
two new variables can do even more than CTS_CORE_CASE_LIST due to
their generality. In the future, the idea is move away from
CTS_CORE_CASE_LIST and also generate XMLs using separate tools
rather than just buildCts.py.

Change-Id: Ib52722861c37e0f4d511f9041928395bcaba5dea
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index d9f3372..66e6232 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -114,6 +114,7 @@
 LOCAL_PROTOC_FLAGS:=
 LOCAL_NO_CRT:=
 LOCAL_PROPRIETARY_MODULE:=
+LOCAL_CTS_TEST_PACKAGE:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.