Include CTS Build Rules

Change-Id: Ieacee8ff6215b22222ea9ea6a1e62fce62daad77
diff --git a/core/config.mk b/core/config.mk
index 47d675a..8c9749e 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -73,6 +73,8 @@
 BUILD_NATIVE_TEST := $(BUILD_SYSTEM)/native_test.mk
 BUILD_HOST_NATIVE_TEST := $(BUILD_SYSTEM)/host_native_test.mk
 
+-include cts/build/config.mk
+
 # ###############################################################
 # Parse out any modifier targets.
 # ###############################################################