I tested "sencha ant clean" and found that it left behind many files the .sass-cache for touch applications.
Sencha Cmd v188.8.131.524
part of Complete version 184.108.40.206
that includes ext-220.127.116.113
that includes touch-2.2.0
To test that I created a fresh workspace, created a touch app and an ext app, built both (the demo code unaltered), then cleaned both using "sencha ant clean" in each app directory. I captured the contents of the file system after it was freshly created, and after building and cleaning. Files are attached that show the file system contents after the workspace and apps were freshly created, and after being built and cleaned. Diff those and you'll see what was left after the clean (the goal is nothing left!). You can see the touch .saas-cache is left in place.
It is important that the clean be as complete as possible. It makes revision control easier and more effective.