[autotest] Add logic to symbolicate dumps using dev server

re-run /usr/local/autotest/utils/build_externals.py before trying to use this
outside the chroot.

BUG=chromium-os:29730
TEST=point local autoserv at a local dev server, run a test that causes a crash; it should symbolicate the crash into a .txt named after the minidump file.

CQ-DEPEND=Ib9d5b0abb73567fd8450db50d3e50d27bdc169f4

Change-Id: Id0d1fd6b4f00e560dd5683d87140ed943697f185
Reviewed-on: https://gerrit.chromium.org/gerrit/21277
Commit-Ready: Chris Masone <cmasone@chromium.org>
Reviewed-by: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
3 files changed