I2P: greatly simplify build recipe
I2P: greatly simplify build recipe

* Use v7-appcompat as a srclib, and don't run 'android update' manually
* Remove prebuilt binaries (ugh) via scandelete
* Join echos
* Simplify the sed commands into a single command, easier to update

f-droid/fdroiddata,f-droid/fdroid-data,f-droid/fdroiddata