Add a faux library libkeymasterfiles to export source.

The library contains nothing, but it exports everything in keymaster as
an include file, enabling it to be #included in other projects.  This is
to make it easy to build keymaster for TLK.

Bug: 24372377
Change-Id: I0f9fd30e2feb1d89a8ff199567ce1ec6b037e236
diff --git a/Android.mk b/Android.mk
index 8aba49a..5a6dbb4 100644
--- a/Android.mk
+++ b/Android.mk
@@ -76,7 +76,7 @@
 LOCAL_SHARED_LIBRARIES := libcrypto libkeymaster_messages
 LOCAL_CFLAGS = -Wall -Werror -Wunused
 LOCAL_CLANG_CFLAGS += -Wno-error=unused-const-variable -Wno-error=unused-private-field
-# Ignore benigh warnings for now.
+# Ignore benign warnings for now.
 LOCAL_CLANG_CFLAGS += -Wno-error=unused-private-field
 LOCAL_MODULE_TAGS := optional
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
@@ -114,6 +114,18 @@
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
 include $(BUILD_SHARED_LIBRARY)
 
+###
+# libkeymasterfiles is an empty library that exports all of the files in keymaster as includes.
+###
+include $(CLEAR_VARS)
+LOCAL_MODULE := libkeymasterfiles
+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)
+
 # Unit tests for libkeymaster
 include $(CLEAR_VARS)
 LOCAL_MODULE := keymaster_tests