Creating an emulator without an ABI specified tries to inform the user which ABIs are available for this platform.
Currently with SDK Tools 23.0.5, I'm getting this output, with "default/" prepended to each name:
[android] /home/chris/android/sdk/tools/android create avd -f -a -s WXGA800 -n hudson_fr-CA_240_WXGA800_android-15 -t android-15
There is more than one system image defined for platform 'android-15'.
Pick an image to use and set it in the 'Target ABI' config field.
Valid ABIs: default/armeabi-v7a, default/x86