Add rules.mk for building in Trusty

Change-Id: Id905b62560f19f7343af801c4da3720178082587
diff --git a/rules.mk b/rules.mk
new file mode 100644
index 0000000..af6dfa2
--- /dev/null
+++ b/rules.mk
@@ -0,0 +1,15 @@
+LOCAL_DIR := $(GET_LOCAL_DIR)
+
+MODULE := $(LOCAL_DIR)
+
+MODULE_SRCS := \
+	$(LOCAL_DIR)/gatekeeper_messages.cpp \
+	$(LOCAL_DIR)/gatekeeper.cpp
+
+GLOBAL_INCLUDES += $(LOCAL_DIR)/include/
+
+MODULE_DEPS := \
+	lib/libc \
+	lib/libc-trusty \
+
+include make/module.mk