llvm_tools: fix LLVM bisection tool.

The changes the LLVM bisection tool to adpat to the new output of "cros
tryjob --json".

BUG=chromium:1203504
TEST=Successfully launched the tool.

Change-Id: I1d6676fb966aee68ce7af177a65de0358a73baf2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2855895
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Jian Cai <jiancai@google.com>
2 files changed