llvm_tools: Add --cq_trybot option to specify cq trybots using cq

The users now can specify one of {llvm,llvm-next,llvm-tot} when
using cq to run the tests with this patch. Invalid cq trybots will
be denied.

BUG=chromium:1072063
TEST=Unittest pass
TEST=crrev.com/c/2163157

Change-Id: Ib1f57267a2e37ebe0e71042e8b24cb2281380f3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2163257
Commit-Queue: Tiancong Wang <tcwang@google.com>
Tested-by: Tiancong Wang <tcwang@google.com>
Reviewed-by: George Burgess <gbiv@chromium.org>
2 files changed