Revert "Switch to LLVM prebuilt tools for ART gtests"

This reverts commit 8070443ce4b31a6787c22490f18f838f8f6ed4be.

Reason for revert: Failing on chrome buildbots.
Test: None
Bug: 137817558

Change-Id: I4cbb4898e859ce33560592dd63cbf4a413048662
9 files changed