[ThinLTO] Clang changes to utilize new pass to handle chains of aliases

Summary:
As with NameAnonGlobals, invoke the new CanonicalizeAliases via clang
when using the new PM.

Depends on D54507.

Reviewers: pcc, davidxl

Subscribers: mehdi_amini, inglorion, steven_wu, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D55620

llvm-svn: 350424