[BuildLibCalls] Noalias annotation

Summary: I think this is better solution than annotating callsites in IC/SLC.

Reviewers: jdoerfert

Reviewed By: jdoerfert

Subscribers: MaskRay, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66217

llvm-svn: 368875