libweave: Ignore out/, third_party/lib and third_party/include files

BUG=brillo:1275
TEST=none

Change-Id: Ic776e50a2db78a5dbbf54361b352320a731b10f9
Reviewed-on: https://chromium-review.googlesource.com/297003
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Trybot-Ready: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>