seedvault/app/build.gradle

import groovy.xml.XmlUtil

apply plugin: 'com.android.application'

android {

    compileSdkVersion 28
    buildToolsVersion '28.0.3'

    defaultConfig {
        minSdkVersion 26
        targetSdkVersion 28
    }

    buildTypes {
        release {
            minifyEnabled false
        }
    }

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

    // optional signingConfigs
    def keystorePropertiesFile = rootProject.file("keystore.properties")
    if (keystorePropertiesFile.exists()) {
        def keystoreProperties = new Properties()
        keystoreProperties.load(new FileInputStream(keystorePropertiesFile))

        signingConfigs {
            release {
                keyAlias keystoreProperties['keyAlias']
                keyPassword keystoreProperties['keyPassword']
                storeFile file(keystoreProperties['storeFile'])
                storePassword keystoreProperties['storePassword']
            }
        }
        buildTypes.release.signingConfig = signingConfigs.release
    }
}

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

// http://www.31mins.com/android-studio-build-system-application/
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 (NullPointerException | FileNotFoundException ex) {
        ex.printStackTrace()
    }
}

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

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