Error building symbol: variable BuildConfig

I addedd ReactNative Facebook SDK. It works great on iOS but on Android it gives me this error when building.

package com.friendster;

import android.app.Application;
import android.util.Log;

import com.facebook.react.ReactApplication;
import com.facebook.react.ReactInstanceManager;
import com.facebook.react.ReactNativeHost;
import com.facebook.react.ReactPackage;
import com.facebook.react.shell.MainReactPackage;

import java.util.Arrays;
import java.util.List;

public class MainApplication extends Application implements ReactApplication {

  private final ReactNativeHost mReactNativeHost = new ReactNativeHost(this) {
    @Override
    protected boolean getUseDeveloperSupport() {
      return BuildConfig.DEBUG;
    }

    @Override
    protected List<ReactPackage> getPackages() {
      return Arrays.<ReactPackage>asList(
          new MainReactPackage()
      );
    }
  };

  @Override
  public ReactNativeHost getReactNativeHost() {
      return mReactNativeHost;
  }
}

Gives me this error:

:app:compileDebugJavaWithJavac
/development/reactnative/FriendsterProject/Friendster-App/android/app/src/main/java/com/friendster/MainApplication.java:20: error: cannot find symbol
      return BuildConfig.DEBUG;
             ^
  symbol: variable BuildConfig
1 error
:app:compileDebugJavaWithJavac FAILED

FAILURE: Build failed with an exception.

Thanks in advance

• React Native version: 0.37.0
• Platform: Android
• Operating System: MacOS