Merge "Create a simple README for bazel darwin prebuilts." am: 59048da6cd am: aa6513f98d am: 11b27bcbac

Original change: https://android-review.googlesource.com/c/platform/prebuilts/bazel/darwin-x86_64/+/1622682

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Iea25cc6ae32b4be3c6d988389c920e79a3c61577