flutter android maven镜像设置 增加打包速度

由于某些原因，flutter android打包往往会很慢，而且容易失败
只需要将android下面的build.gradle 段时的 repositories maven源替换成国内镜像即可。

buildscript {
    ext.kotlin_version = '1.5.20'
    repositories {
        // google()
        // mavenCentral()
        maven{ url 'https://maven.aliyun.com/repository/central' }
        maven{ url 'https://maven.aliyun.com/repository/public' }
        maven{ url 'https://maven.aliyun.com/repository/google' }
        maven{ url 'https://maven.aliyun.com/repository/gradle-plugin' }      
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:7.0.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
    maven{ url 'https://maven.aliyun.com/repository/central' }
    maven{ url 'https://maven.aliyun.com/repository/public' }
    maven{ url 'https://maven.aliyun.com/repository/google' }
    maven{ url 'https://maven.aliyun.com/repository/gradle-plugin' }    
    }
}