memento_updater: Add the C++ version (src/) into build results

To include the new updater into system, we have to include src directory into
Makefile.

BUG=chrome-os-partner:21938
TEST=emerge-link memento_softwareupdate # passed

Change-Id: I5a72d33095865b2d5d688015d793640085dd9f0b
Reviewed-on: https://chromium-review.googlesource.com/178380
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Rong Chang <rongchang@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>
1 file changed