import groovy.io.FileType
import java.nio.file.Paths
import net.sf.jasperreports.engine.JasperCompileManager

final String srcDir = args ? args[0] : ''
final String outDir = args.length > 1 ? args[1] : srcDir

new File(srcDir).traverse(type : FileType.FILES, nameFilter: ~/(?i).*.jrxml$/) { file ->
    String relative = new File(srcDir).toURI().relativize(file.toURI()).getPath()
    def srcFile = Paths.get(srcDir, relative)
    def outFile = Paths.get(outDir, relative)
    new File(outFile.getParent().toString()).mkdirs()
    JasperCompileManager.compileReportToFile  srcFile.toString(), outFile.toString().replaceAll(~/(?i).jrxml$/, ".jasper")
}

ext {
    jrtemplateDir = "$projectDir/jrtemplate"
}
...
configurations {
    groovyScript
    jasperreports
}

dependencies {
    groovyScript(
            localGroovy()
    )
    jasperreports(
        "org.eclipse.jdt.core.compiler:ecj:4.5.1",
        "net.sf.jasperreports:jasperreports:5.6.1",
    }
}

task compileJasperReports(group: 'build', description: 'Compiling JasperReports files', dependsOn: ["build"]) {
    doLast {
        javaexec {
            main = 'groovy.ui.GroovyMain'
            classpath = configurations.groovyScript
            classpath += configurations.jasperreports
            classpath += sourceSets.main.runtimeClasspath 
            classpath += configurations.compile

            standardOutput = System.out

            args = ["${projectDir}/gradle/scripts/JasperCompile.groovy", "${jrtemplateDir}"]
        }
    }
}

task copyAllDepsToLibs() {
    copy {
        from configurations.runtime
        from configurations.compile
        into "${projectDir}/libs"
    }
}

productFlavors {
    someFlavor {
        configure(this, 42, 'foo', true)
    }
    anotherFlavor {
        configure(this, 52, 'bar', false)
    }
}

import com.android.build.gradle.internal.dsl.ProductFlavor


productFlavors {
    someFlavor { flavor ->
        configureFlavor(flavor, 'com.example.app', 'Something')
    }
}

static void configureFlavor(ProductFlavor flavor, String appId, String someBuildConfigField) {
    flavor.setApplicationId(appId)
    flavor.buildConfigField 'String', 'SOME_CONST_NAME', "\"$someBuildConfigField\""
}