New builds not overwriting old files?

I did 4 android builds in a row. No matter what I do the same old code ends up in the apk. I verified i don’t have the old code anymore under my www/. But then i grep through android/build/* and sure enough it had old version of my main app.js file.

I can’t see any documentation on how one does the equivalent of ‘make clean’. What does one have to do other than manually blow away the build folder?