[UBSan] Make stacktrace-matching CHECK-lines in tests Linux-specific.

Darwin doesn't yet allow to print stack trace, as it lacks the slow
unwinder. This is one more attempt to fix vptr.cpp on Mac OS X.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@236195 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed