New source package platform-tools-latest

On the lines of our current WiP sdk-latest package, we want to create a package in the same vein for platform-tools to make things easier.

Helped by the new 'platform-tools' tags,

https://android.googlesource.com/platform/manifest/+/refs/tags/platform-tools-30.0.3

And then you can get upstream platform-tools, run adb --version, which'll include "version 30.0.3-6597393"

That last bit is the build id, from which we get https://ci.android.com/builds/submitted/6597393/sdk/latest - which has all the artifacts we'd need.

https://dl.google.com/android/repository/platform-tools_r30.0.3-linux.zip