In Android SDK r22, aapt was moved from platform-tools/ to build-tools/17.0.0/. This causes Android Emulator plug-in to stop working with the following error:
[android] Required Android tools not found in PATH; cannot continue
Putting $ANDROID_HOME/build-tools/17.0.0/ in the path variable doesn't resolve the issue.
The temporary workaround is to create a soft-link under $ANDROID_HOME/platform-tools/ to $ANDROID_HOME/build-tools/17.0.0/aapt