We have 2 versions of the Guava library in our source tree:

The one in external/guava is used for the platform. It has the module
name "guavalib".

The one in prebuilts/tools/common/guava-tools is shipped in the
SDK/tools/lib/ folder. It has the module name guava-tools.

These are maintained separately because the external/ version is
branched with the platform, and the prebuilts/tools/ version is
branched with the tools, and these have different release schedules
and branches.