[Macros] Ensure to kill and reap plugin process
`llvm::sys::Wait(process, /*SecondsToWait=*/0)` perform a non-blocking
`wait`. That means the plugin goes a zombie if it hasn't exited.
Set `SecondsToWait` 1 so it wait for 1 second and kill it on the time
out. Usually, when the pipe is closed, the plugins detect the EOF in
stdin and exits immediately, fo the parent process usually don't wait
for the timeout.
rdar://148110944
