Made llvm-cfi-verify not execute unit tests on non-x86 builds.

Patched out from D38427.

Reviewers: vlad.tsyrklevich

Reviewed By: vlad.tsyrklevich

Subscribers: llvm-commits, kcc, pcc, mgorny

Differential Revision: https://reviews.llvm.org/D39197

llvm-svn: 316375