Android Build fail: Execution failed for task ':transformClassesAndResourcesWithProguardForRelease'.

## Is it a security issue?

no

## What did you do?

I create a empty unity project, import ‘line_sdk_unity_1.1.6.unitypackage’, and add "implementation 'androidx.legacy:legacy-support-v4:1.0.0'" in 'mainTemplate.gradle'. Then set 'minifyEnabled true' and 'useProguard true'.
Then build, it show : Gradle build failed.
if don't add "implementation 'androidx.legacy:legacy-support-v4:1.0.0'" or set 'useProguard false', it will build success.

## What did you expect?

My project need add "implementation 'androidx.legacy:legacy-support-v4:1.0.0'" and set 'useProguard true'.
I hope it can build success.

## What happened actually?

I added my log as an attachment

## Your environment?

> Some information of the environment in which the issue happened. LINE SDK version, Unity version, Android version, iOS version, etc.
LINE SDK version: line_sdk_unity_1.1.6.unitypackage
Unity version: unity 2017.4.30f1
Android version: Minimum API Level 17, Target API Level 29, Build Gradle: 3.2.0

## Sample project

it's a empty unity project, then import ‘line_sdk_unity_1.1.6.unitypackage’ and modify mainTemplate.gradle
[mainTemplate.txt](https://github.com/line/line-sdk-unity/files/7230684/mainTemplate.txt)
[log.txt](https://github.com/line/line-sdk-unity/files/7230685/log.txt)

Supplementary notes: my actually project also add other SDK. For example appsflyer, firebase, facebook, gms, etc.