Flags common for native tests

With the CL, "include $(BUILD_NATIVE_TEST)" to build native test;
"include $(BUILD_HOST_NATIVE_TEST)" to build a host native test.

Change-Id: Icdbbcf906cd4c5c35e65962897490052cd051102
diff --git a/core/envsetup.mk b/core/envsetup.mk
index 87ac2f6..da9dd28 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -237,6 +237,7 @@
 TARGET_OUT_DATA_KEYCHARS := $(TARGET_OUT_KEYCHARS)
 TARGET_OUT_DATA_ETC := $(TARGET_OUT_ETC)
 TARGET_OUT_DATA_STATIC_LIBRARIES:= $(TARGET_OUT_STATIC_LIBRARIES)
+TARGET_OUT_DATA_NATIVE_TESTS := $(TARGET_OUT_DATA)/nativetest
 
 TARGET_OUT_UNSTRIPPED := $(PRODUCT_OUT)/symbols
 TARGET_OUT_EXECUTABLES_UNSTRIPPED := $(TARGET_OUT_UNSTRIPPED)/system/bin