UserspaceEmulator: Move exit() syscall logging to debug output

We want the emulated program to appear without noise in the terminal.

DevTools/UserspaceEmulator/Emulator.cpp

@@ -409,7 +409,7 @@ u32 Emulator::virt$read(int fd, FlatPtr buffer, ssize_t size)
 
 void Emulator::virt$exit(int status)
 {
- out() << "exit(" << status << "), shutting down!";
+ dbg() << "exit(" << status << "), shutting down!";
  m_exit_status = status;
  m_shutdown = true;
 }