Add LOCAL_COMPATIBILITY_SUPPORT_FILES to copy arbitrary CTS support files.

LOCAL_COMPATIBILITY_SUPPORT_FILES is a list of <src>:<dest>,
where <src> is relative to LOCAL_PATH and <dest> is relative to the
suite's testcases out directory.
We keep the rule to auto-detect AndroidTest.xml and DynamicConfig.xml,
so you don't need to modify the existing cts Android.mks.

Bug: 24139963
Bug: 21762834
Change-Id: Iecb83fcbcf8c7575c27802bfd773e4134aec39d5
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 88b99e2..f0b2a91 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -148,6 +148,7 @@
 LOCAL_PRIVILEGED_MODULE:=
 LOCAL_MODULE_OWNER:=
 LOCAL_COMPATIBILITY_SUITE:=
+LOCAL_COMPATIBILITY_SUPPORT_FILES:=
 LOCAL_CTS_TEST_PACKAGE:=
 LOCAL_CTS_TEST_RUNNER:=
 LOCAL_CLANG:=