For CleanseCrashInput, discards stdout output anyway since it is not used.
Also giving TempPath a prefix representing the work it is doing.
These changes are to defend against aggressive PID recycle on windows to reduce the chance of contention on files.
Using pipe instead of file also workaround the problem that when the
process is spawned by llvm-lit, the aborted process keeps a handle to the
output file such that the output file can not be removed. This will
cause random test failures.