[Android] Add xwalk_app_template_apk to xwalk_builder's dependency

Canary management framework will try to package XWalkAppTemplate.apk
for its output. So add xwalk_app_template_apk to xwalk_builder's
dependency to make sure it will be built.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2465