WIP: upgrade to the latest version of Android SDK "tools"

We have been frozen on tools_r25.2.5-linux.zip for the longest time because the buildserver provisioning required android update sdk to work. This replaces that with fdroid/sdkmanager, so the buildserver is free to have any version of "tools" installed, since none of the buildserver's setup processes need anything from "tools" any more.

@proletarius101 I think this will achieve what you were trying to do in fdroiddata!11367 (merged)