Require an android_local_tools_repository stanza in the WORKSPACE file so that Bazel finds Android tools and update the tools themselves to handle their new location.

This paves the way for eventually referencing every tool this way.

We have to figure out if android_http_tools_repository is the right way to distribute the Android tools, but now that we don't have a binary distribution yet, it's not an immediate problem.

This will break existing users of Android support in Bazel, whom I'll inform over bazel-discuss.

Fixes #384.

--
MOS_MIGRATED_REVID=101456190