run: pass Ctrl+C to GDB when using -D

run

@@ -195,6 +195,12 @@ ${extra_flags} \
 "
   fi
 else
+  if [ -z "$debug_vm" ]; then
+    serial_monitor='-serial mon:stdio \
+'
+  else
+    serial_monitor=
+  fi
   if "$kvm"; then
     extra_flags="${extra_flags} -enable-kvm"
   fi
@@ -205,9 +211,9 @@ ${debug_vm} \
 -device rtl8139,netdev=net0 \\
 -gdb tcp::1234 \\
 -m '${memory}' \\
--serial mon:stdio \\
 -monitor telnet::45454,server,nowait \\
 -netdev user,hostfwd=tcp::45455-:45455,hostfwd=tcp::45456-:22,id=net0 \\
+${serial_monitor} \
 -smp '${cpus}' \\
 -trace 'enable=${trace_type},file=${qemu_out_dir}/trace.bin' \\
 -virtfs 'local,path=${p9_dir},mount_tag=host_scratch,security_model=mapped,id=host_scratch' \\