am 3a9aa008: am def30fc2: Clarify the use of --boot-dirs in the header comment.

Merge commit '3a9aa008c9d4bfe29d3e35658a7f227bc4340b43'

* commit '3a9aa008c9d4bfe29d3e35658a7f227bc4340b43':
  Clarify the use of --boot-dirs in the header comment.