Use single module for clang runtime libraries

The clang prebuilts now provide a single module with per-architecture
variants instead of a module per architecture.

Bug: 220019988
Test: m checkbuild
Change-Id: I39e2cf8ae14edf8510276dab38011afaef85822c
(cherry picked from commit 386ee59a)
Merged-In:I39e2cf8ae14edf8510276dab38011afaef85822c