[cfi-verify] Fix unittest failures w/o x86 target

The llvm-cfi-verify unit tests fail if LLVM is built without the X86
target, disable the unit tests from being built unless X86 is enabled
for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315556 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed