Resolve #1168 by way of a makeshift, in absence of better isolation of the ksp environment.

[cgruber]

Guava is used in a lot of different environments. This causes classloader problems at times, in that parts of guava get loaded early, but other parts are loaded late, in other classloaders, and you end up with conflicts around the boundary.

In #1168 @xinzhengzhang suggested a fix (implemented here) to preload guava, so it is fully loaded and can be resolved without crossing classloader boundaries.

While better classloader isolation is preferable, this at least unblocks folks while a more robust isolation scheme is explored.

[cgruber]

Note - this makeshift isn't working, regrettably. It may require a full fix to the isolation. (I'm also talking to the Dagger project about better isolation of their deps via shading - the dagger-compiler should be shaded, so I'm not sure what's up there).