android-sdk: Certain files are lost on upgrade

Currently, the android-sdk will install the platform-tools and build-tools into 2 directories that should be outside of the android-sdk cellar, but are not.

Because of this, on an upgrade of the android-sdk, any installations of the platform-tools and build-tools will be lost.

The attached patch fixes this by adding the two additional directories to the existing list of preserved data directories.
Last thing: caveats need updated now, right?