There appears to be a problem with one of your icon files:
Execution failed for task ':mergeArmv7ReleaseResources'. > .../cordova_project/platforms/android/res/drawable-xhdpi/icon.png: Error: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '.../android-sdk/build-tools/21.1.2/aapt'' finished with non-zero exit value 42
points to this:
Try removing all icons from your project to see if the build works with no icons.