app/build.gradle

import groovy.xml.XmlUtil

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    buildToolsVersion '28.0.0'

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    lintOptions {
        abortOnError false
    }
    compileOptions {
        targetCompatibility 1.8
        sourceCompatibility 1.8
    }
}

gradle.projectsEvaluated {
    tasks.withType(JavaCompile) {
        options.compilerArgs.add('-Xbootclasspath/p:app/libs/android.jar:app/libs/libcore.jar')
    }
}

preBuild {

    doLast {
        def imlFile = file(project.name + ".iml")

        try {
            def parsedXml = (new XmlParser()).parse(imlFile)
            def jdkNode = parsedXml.component[1].orderEntry.find { it.'@type' == 'jdk' }
            parsedXml.component[1].remove(jdkNode)

            def sdkString = "Android API " + android.compileSdkVersion.substring("android-".length()) + " Platform"
            new Node(parsedXml.component[1], 'orderEntry', ['type': 'jdk', 'jdkName': sdkString, 'jdkType': 'Android SDK'])
            XmlUtil.serialize(parsedXml, new FileOutputStream(imlFile))

        } catch (FileNotFoundException ex) {
            ex.printStackTrace()
        }
    }
}

dependencies {
    compileOnly fileTree(include: ['android.jar', 'libcore.jar'], dir: 'libs')

    compile group: 'commons-io', name: 'commons-io', version: '2.6'
}