llvm_tools: add -Werror log fetching functionality

This allows us to fetch -Werror logs from CLs, or specific
cq-orchestrator runs. These are unpacked so one can later `analyze`
them.

BUG=b:316172255
TEST=Ran (slightly modified) on a CQ that produced many Clang crash
TEST=artifacts.

Change-Id: Ice9a142a98951d7baf79fd8509b6be0b91c10a19
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/5296915
Commit-Queue: George Burgess <gbiv@chromium.org>
Reviewed-by: Ryan Beltran <ryanbeltran@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
3 files changed