cpp11-migrate: turn off PID-based perf data filenames

Getting PIDs on Windows is broken. Proper fix is simple but requires testing so
just disabling PID-based file names for now.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@183154 91177308-0d34-0410-b5e6-96231b3b80d8