Add static gatekeeper library

Add a static library that exports gatekeeper source so that it can
be used in the Gatekeeper TLK task.

Change-Id: I66abcdba860a75c29bdc5a67ad8f0aee5de872cf
(cherry picked from commit 9be92ed1b5a470cb824516a9b950256a138533f8)
diff --git a/Android.mk b/Android.mk
index 20ebbcb..0d7e1b6 100644
--- a/Android.mk
+++ b/Android.mk
@@ -31,4 +31,17 @@
 LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
 include $(BUILD_SHARED_LIBRARY)
 
+###
+# libgatekeeper_static is an empty static library that exports
+# all of the files in gatekeeper as includes.
+###
+include $(CLEAR_VARS)
+LOCAL_MODULE := libgatekeeper_static
+LOCAL_EXPORT_C_INCLUDE_DIRS := \
+        $(LOCAL_PATH) \
+        $(LOCAL_PATH)/include
+LOCAL_MODULE_TAGS := optional
+LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
+include $(BUILD_STATIC_LIBRARY)
+
 include $(call first-makefiles-under,$(LOCAL_PATH))