[UBSan] Temporarily disable checks for stack traces in UBSan reports on Darwin
to make the tests green.
Slow stack unwinding is disabled in libsanitizer on Darwin now.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@216657 91177308-0d34-0410-b5e6-96231b3b80d8