Add venv wrapper and reset notice for GD32 flasher

Add an executable bash wrapper at common/scripts/gd32/flash that bootstraps a Python venv (using python3), installs/updates pip and pyserial, and execs flash.py; includes checks and a helpful error if python/venv is missing. Also add a brief print in common/scripts/gd32/flash.py to instruct users to manually reset the MCU before the next bootloader session.

Author: vanvught

common/scripts/gd32/flash

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -euo pipefail
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+PYTHON="${PYTHON:-python3}"
+command -v "$PYTHON" >/dev/null 2>&1 || PYTHON=python
+command -v "$PYTHON" >/dev/null 2>&1 || { echo "No python found (need python3)"; exit 1; }
+
+if [[ ! -x "$DIR/venv/bin/python" ]]; then
+  "$PYTHON" -m venv "$DIR/venv" || {
+    echo "Failed to create venv. On Debian/Ubuntu install: python3-venv" >&2
+    exit 1
+  }
+  "$DIR/venv/bin/python" -m pip install -q -U pip
+  "$DIR/venv/bin/python" -m pip install -q pyserial
+fi
+
+exec "$DIR/venv/bin/python" "$DIR/flash.py" "$@"
+

common/scripts/gd32/flash.py

@@ -45,6 +45,7 @@ def close(self):
             time.sleep(0.1)
             self.port.rts = False
             self.port.close()
+            print("Done. Reset the MCU manually before the next bootloader session.")
 
     def enter_bootloader(self):
         """Enter ROM bootloader mode using DTR/RTS"""