toolchain-utils: Update README.md for llvm_tools.

This corrects an error, a typo, and an omission I discovered in the
README.md instructions.

BUG=None
TEST=None

Change-Id: I19c46d87bf326c9ab320dc7bb23b4a8dae5573fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2416246
Auto-Submit: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Commit-Queue: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
diff --git a/llvm_tools/README.md b/llvm_tools/README.md
index 9c4a9c0..d7c2016 100644
--- a/llvm_tools/README.md
+++ b/llvm_tools/README.md
@@ -278,6 +278,7 @@
   --last_tested /abs/path/to/last_tested_file.json \
   --extra_change_lists 513590 1394249 \
   --options latest-toolchain nochromesdk \
+  --chroot_path /path/to/chromeos/chroot \
   --builder eve-release-tryjob
 ```
 
@@ -554,8 +555,8 @@
 ### `bisect_clang_crashes.py`
 
 This script downloads clang crash diagnoses from
-gs://chrome-toolchain-artifacts/clang-crash-diagnoses and send them to 4c for
-bisectiton.
+gs://chromeos-toolchain-artifacts/clang-crash-diagnoses and send them to 4c for
+bisection.
 
 Usage example: