[tools] Allow for debugging with GDB cmd shell

Author: salkinium

tools/modm_tools/gdb.md

@@ -56,8 +56,9 @@ python3 -m modm_tools.gdb --elf path/to/project.elf -x modm/gdbinit --ui=tui \
 
 (\* *only ARM Cortex-M targets*)
 
-Currently two UIs are implemented for debugging:
+Currently three UIs are implemented for debugging:
 
+- `--ui=cmd`: No UI, only the GDB command shell.
 - `--ui=tui`: Text-based UI in your shell.
 - `--ui=gdbgui`: Web-based UI in your browser, based on [gdbgui][].
 

tools/modm_tools/gdb.py

@@ -30,6 +30,9 @@ def _gdb_command(backend, source=None, config=None, commands=None, ui=None):
     if ui is None:
         return f"{gdb} -nx -nh -batch {args} {source}"
 
+    elif "cmd" in ui:
+        return f"{gdb} {args} {source}"
+
     elif "tui" in ui:
         return f'{gdb} -tui -ex "layout split" -ex "focus cmd" {args} -ex "refresh" {source}'