cthd_engine::giveup_thermal_control is not signal safe

[benzea]

This is indirectly called by the signal handler:

• sig_int_handler
• thd_engine_terminate
• process_terminate
• giveup_thermal_control

I don't really get the signal handling code though, why sleep for 1 second? Is that assuming that a different thread is still running and the mainloop can continue to work?