llvm_tools: add git_llvm_rev notes.

BUG=None
TEST=None

Change-Id: I64dd7b2e8a5e5210d3a53bb1de5c510072715aa4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2113170
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
1 file changed