Android : how to change the android-gradle-productFlavours - package name form jenkin property

I've convert my android project build from (maven) to Gradle.

Old Project Struct Was

Android Lib Project (as apklib)
Andlrid Template build Project (use the above anroid Lib project as a dependency)

I'm using the Jenkins CI to build and release the apk for different clients. only thing i need to have a different package name for each apk. so i used the

<renameManifestPackage>${app.pkg.name}</renameManifestPackage>

and passing this "app.pkg.name" from jenkin as a property.

My problem is how do can i achieve the same with gradle.

apply plugin: 'com.android.application'

android {
    compileSdkVersion 20
    buildToolsVersion "20.0.0"

    defaultConfig {
        applicationId "myapp.myappbasetemplate"
        minSdkVersion 15
        targetSdkVersion 20
        versionCode 1
        versionName "1.0"
    }

    signingConfigs {
        debug {
            storeFile file("debug.keystore")
        }

        release {
            storeFile file("../keystore/myproject.keystore.")
            storePassword "*******"
            keyAlias "check"
            keyPassword "********"
        }
    }
    buildTypes {
        release {
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.release
            debuggable false
            zipAlign true
        }
    }

    productFlavors {
        festival {
            packageName "${newPackageName}"
            versionCode 20
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
}