Merge "Rename abazel() to bazel(), give a warning if clobbering an existing...

Merge "Rename abazel() to bazel(), give a warning if clobbering an existing Bazel, and have it call tools/bazel (aka build/bazel/bazel.sh) to start Bazel." am: d6bcec35

Original change: https://android-review.googlesource.com/c/platform/build/+/1473018

Change-Id: I4fb2b96b82a6c71d068b387ba0e605da39b1c406