build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.0'
        classpath 'me.tatarka:gradle-retrolambda:3.1.0'
        classpath 'com.google.gms:google-services:3.0.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

def configsPrivateFile = new File('configs.private.properties')
def configsCommonFile = new File('configs.common.properties')

Properties props = new Properties()
try {
    if (configsPrivateFile.exists()) {
        props.load(configsPrivateFile.newDataInputStream())
    } else if (configsCommonFile.exists()) {
        props.load(configsCommonFile.newDataInputStream())
    } else {
        throw new GradleException("Configs file not exists");
    }
} catch (Exception ignored) {
    throw new GradleException("Can't load configs file");
}

ext.apiKeyProd = props.getProperty("API_KEY_PRODUCTION")
ext.apiKeyDebug = props.getProperty("API_KEY_DEBUG")
ext.fabricApiKey = props.getProperty("FABRIC_API_KEY")