DumpPreviousStacktrace dumps the previous human readable stacktrace to fd, which is set by SetSignalDumpToFd.

DumpSignalTo redirects log to fd, -1 if not set; muted if < 0.

DumpStacktraceTo set dump file path of stacktrace when signal is triggered "*.stacktrace.dump" under a temp dir if not set.

Notify act as signal.Notify, which invokes the Go signal handler.

PreviousStacktrace returns a human readable stacktrace.

SetSigInvokeChain sets a rule to raise signal to {to} and wait until {wait}, done with sleep {sleepInSeconds}s.