Buck: Clarify how to delete the build cache

Inspired-By: David Ostrovsky <david@ostrovsky.org>
Change-Id: I1e98d9bcf63c289a52ab4643d2cc047622209e5a
Remove leading `$` from command examples in Buck documentation

Some of the example commands have a leading `$`. Most of them don't.

Remove them to make it consistent.

Change-Id: I6a425d278e7b01c103863f9c7df1e43401e5b063
Buck local_jar: Clarify how to overcome stale cache problem

Change-Id: I2a74c24551804dd5b6dac7d1d801aebc8c5dbde8