message: Fix documentation of the ccache part
  This patch fixes the comment that isn't fixed altogether in commit
diff: @@ -321,8 +321,8 @@ parts:
  # This pseudo part setups Compiler cache(ccache) to the stage dir.
  #
  - # To use it simply add a dependency to this part and prepend
  - # "$SNAPCRAFT_STAGE"/bin to the command search PATHs
  + # To use it simply add a dependency to this part for every part you'd
  + # prefer caching
  ccache:
  after:
  - gcc-6
  