Add TWRP app install via TWRP recovery

Note: I will have to add a build flag for excluding the app later for
watches and maybe Android TV. I will also have to add support in the
tablet and watch layouts later. I will merge this for the initial roll out
to select devices and finish up later.

Change-Id: Ia4ce5522fae542afa1539b10c0691315392a19ab
diff --git a/prebuilt/Android.mk b/prebuilt/Android.mk
index 67aa86b..b5891ac 100644
--- a/prebuilt/Android.mk
+++ b/prebuilt/Android.mk
@@ -501,3 +501,12 @@
 	LOCAL_SRC_FILES := $(LOCAL_MODULE)
 	include $(BUILD_PREBUILT)
 endif
+
+#TWRP App "placeholder"
+include $(CLEAR_VARS)
+LOCAL_MODULE := me.twrp.twrpapp.apk
+LOCAL_MODULE_TAGS := eng
+LOCAL_MODULE_CLASS := RECOVERY_EXECUTABLES
+LOCAL_MODULE_PATH := $(TARGET_RECOVERY_ROOT_OUT)/sbin
+LOCAL_SRC_FILES := $(LOCAL_MODULE)
+include $(BUILD_PREBUILT)