Doc: Improve debugging doc with Qemu demo

FreeRTOS/Demo/CORTEX_M3_MPS2_QEMU_GCC/Readme.md

@@ -112,17 +112,26 @@ the string contains “OK” and the current tick count. If an error has been
 detected, then the string contains a message that indicates which task
 reported the error.
 
+
 ## How to start debugging
-1. gdb
-<P>
-Append the -s and -S switches to the previous command (qemu-system-arm)<br>
--s: allow gdb to be attached to the process remotely at port 1234 <br>
--S: start the program in the paused state <br>
+1. Build the debug version by using `DEBUG=1`:
+```
+$ make DEBUG=1
+```
+2. Run the binary with `-s` and `-S` flags:
+```
+$ sudo qemu-system-arm -machine mps2-an385 -monitor null -semihosting \
+        --semihosting-config enable=on,target=native \
+        -kernel ./build/RTOSDemo.axf \
+        -serial stdio -nographic -s -S
+```
+The options:
+`-s` allows gdb to be attached to the process remotely at port 1234
+`-S` starts the program in the paused state.
 
-run: (make sure you build the debug version)
+3. Open another terminal to run GDB and connect to the process:
 ```
 $ arm-none-eabi-gdb -q ./build/RTOSDemo.axf
-
 (gdb) target remote :1234
 (gdb) break main
 (gdb) c