Android : duplicate files during packaging of APK, libpjsua2.so

I got this error Duplicate files during packaging of APK app-debug-unaligned.apk when migrate project from Eclipse to Android studio:

:app:compileDebugJava UP-TO-DATE
:app:preDexDebug UP-TO-DATE
:app:dexDebug UP-TO-DATE
:app:processDebugJavaRes UP-TO-DATE
:app:validateDebugSigning
:app:packageDebug
Error:duplicate files during packaging of APK C:\Users\aaa\AndroidStudioProjects\Pjsua2\app\build\outputs\apk\app-debug-unaligned.apk
    Path in archive: lib/armeabi/libpjsua2.so
    Origin 1: C:\Users\aaa\AndroidStudioProjects\Pjsua2\app\src\main\jniLibs\armeabi\libpjsua2.so
    Origin 2: C:\Users\aaa\AndroidStudioProjects\Pjsua2\app\build\intermediates\ndk\debug\lib\armeabi\libpjsua2.so
You can ignore those files in your build.gradle:
    android {
      packagingOptions {
        exclude 'lib/armeabi/libpjsua2.so'
      }
    }
Error:Execution failed for task ':app:packageDebug'.
> Duplicate files copied in APK lib/armeabi/libpjsua2.so
    File 1: C:\Users\aaa\AndroidStudioProjects\Pjsua2\app\src\main\jniLibs\armeabi\libpjsua2.so
    File 2: C:\Users\aaa\AndroidStudioProjects\Pjsua2\app\src\main\jniLibs\armeabi\libpjsua2.so
Information:BUILD FAILED

I tried to change build.gradle, but anything get same error. My build.gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 15
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "org.pjsip.pjsua2.app"
        minSdkVersion 11
        targetSdkVersion 15

        ndk {
            moduleName "libpjsua2"
        }
    }

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

Please help me fix.