[Driver] Use the per-API level Android library directories.

Summary:
Android sysroots contain libraries for each OS version, as well as a
handful of unversioned libraries in the typical multiarch directory.

Reviewers: srhines, eugenis, george.burgess.iv

Reviewed By: eugenis

Subscribers: javed.absar, cfe-commits

Differential Revision: https://reviews.llvm.org/D45290

llvm-svn: 330213