Add SigningConfig to release type for application subproject

build.gradle

subprojects { subproject ->
    afterEvaluate {

        if (subproject.plugins.hasPlugin('com.android.application')){
            android {

                signingConfigs {
                    release {
                        storeFile file("key.jks")
                        storePassword "keykey"
                        keyAlias "key"
                        keyPassword "keykey"
                    }
                }

                buildTypes.release {
                    signingConfig signingConfigs.release
                }
            }
        }
    }
}