cbuildbot: enable deduping of uploaded symbols

BUG=chromium:209442
TEST=`./buildbot/run_tests` passes
TEST=`cbuildbot daisy-release` works (checked upload symbols stage)
CQ-DEPEND=CL:185622

Change-Id: Ic95c910608ed27a3523ed32713fd81b2ae2a50ab
Reviewed-on: https://chromium-review.googlesource.com/186381
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
1 file changed