Gradle build issue

This is the code i use to build using android-ndk from gradle. For this add ndk directory path in gradle.properties ie . add ndkdir=/home/user/android-ndk-r9d and put all jni files in a folder native in src/main/ as you can see from code posted below. It will create jar with native libs which you can use normally as in System.loadLibrary("library");

dependencies {
    compile fileTree(dir: "$buildDir/native-libs", include: '*.jar')
}

task ndkBuild(type: Exec) {
    commandLine "$ndkdir/ndk-build", "--directory", "$projectDir/src/main/native", '-j', Runtime.runtime.availableProcessors(),
            "APP_PLATFORM=android-8",
            "APP_BUILD_SCRIPT=$projectDir/src/main/native/Android.mk",
            "NDK_OUT=$buildDir/native/obj",
            "NDK_APP_DST_DIR=$buildDir/native/libs/\$(TARGET_ARCH_ABI)"
}

task nativeLibsToJar(type: Zip, description: 'create a jar with native libs') {
    destinationDir file("$buildDir/native-libs")
    baseName 'native-libs'
    extension 'jar'
    from fileTree(dir: "$buildDir/native/libs", include: '**/*.so')
    into 'lib/'
}

tasks.withType(JavaCompile) {
    compileTask -> compileTask.dependsOn nativeLibsToJar
}

nativeLibsToJar.dependsOn 'ndkBuild'