That error specifies that there is a plugin in your app that required the android app to be compiled with gradle not ant. To specify that you would like the app to be built with gradle add the following to your config.xml:
<preference name="android-build-tool" value="gradle" />
I could build the app, however, I get another error related to the crosswalk plugin. I'll post it below but I'll delet it if you think that I need to open a new discussion.
Build Date: 2016-04-01 17:11:15 +0000
Build option --'' not recognized (ignoring).
Running: /project/gradlew cdvBuildRelease -b /project/build.gradle -Dorg.gradle.daemon=true -PcdvBuildMultipleApks=false
FAILURE: Build failed with an exception.
Script '/project/cordova-plugin-crosswalk-webview/gameproject-xwalk.gradle' line: 77
* What went wrong:
A problem occurred evaluating script.
> Could not find property 'xwalkMultipleApk' on root project 'project'.
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
Total time: 2.412 secs
Error code 1 for command: /project/gradlew with args: cdvBuildRelease,-b,/project/build.gradle,-Dorg.gradle.daemon=true,-PcdvBuildMultipleApks= false
I don't know what that means. Maybe I'm using a wrong plugin.
An extra question: It's better to use crosswalk?