Cache invalidation for AARCH64. Disabled for Apple for now as requested
by Tim Northover. Written by Matt Thomas.

Differential Revision: http://llvm-reviews.chandlerc.com/D2631


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200317 91177308-0d34-0410-b5e6-96231b3b80d8