Android.mk: Download prebuilt apk instead of building it

* With the upcoming changes, and the increasing number of external
  libraries being used, plus the usage of Kotlin, it's getting harder
  and harder to build this with the AOSP build system.
* It's best to leverage the existing gradle build system instead,
  and use the apk that builds.
* Add a script which downloads the apk matching the tag if a tag is
  checked out, otherwise downloads the latest.

.gitignore

@@ -46,4 +46,7 @@ gradle-app.setting
 .DS_Store
 
 ## Android
-gen/
+gen/
+
+## Prebuilt
+Backup.apk

Android.mk

@@ -17,19 +17,14 @@ LOCAL_SRC_FILES := $(LOCAL_MODULE)
 include $(BUILD_PREBUILT)
 
 include $(CLEAR_VARS)
-LOCAL_MODULE_TAGS := optional
-LOCAL_PREBUILT_STATIC_JAVA_LIBRARIES := \
-    commons-io:../../libs/commons-io-2.6.jar
-include $(BUILD_MULTI_PREBUILT)
 
-include $(CLEAR_VARS)
-LOCAL_PACKAGE_NAME := Backup
-LOCAL_MODULE_TAGS := optional
-LOCAL_REQUIRED_MODULES := permissions_com.stevesoltys.backup.xml whitelist_com.stevesoltys.backup.xml
-LOCAL_PRIVILEGED_MODULE := true
-LOCAL_PRIVATE_PLATFORM_APIS := true
+backup_root := $(LOCAL_PATH)
+
+$(backup_root)/Backup.apk:
+	cd $(backup_root) && ./download.sh
+
+LOCAL_MODULE := Backup
+LOCAL_SRC_FILES := Backup.apk
 LOCAL_CERTIFICATE := platform
-LOCAL_STATIC_JAVA_LIBRARIES := commons-io
-LOCAL_SRC_FILES := $(call all-java-files-under, java)
-LOCAL_RESOURCE_DIR := $(LOCAL_PATH)/res
-include $(BUILD_PACKAGE)
+LOCAL_MODULE_CLASS := APPS
+include $(BUILD_PREBUILT)

download.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# 
+# Script to download apk from github releases
+
+BASE_URL="https://github.com/stevesoltys/backup/releases"
+APK="app-release-unsigned.apk"
+VERSION="latest/download"
+TAG=$(git tag -l --points-at HEAD)
+
+if [ ! -z ${TAG} ]; then
+	VERSION="download/${TAG}"
+fi
+
+curl -L ${BASE_URL}/${VERSION}/${APK} > Backup.apk