Update README with additional instructions am: 7fc3494f6a am: 784267f9ed am: 187eb9d449 am: dfdcf0f9fc

Original change: https://android-review.googlesource.com/c/platform/build/pesto/+/1701745

Change-Id: I4838d23f0d92a3db9b89393781cf84fa399ba09b