Enhance checks for invalid keyboard build targets (#26122)

Co-authored-by: フィルターペーパー <76888457+filterpaper@users.noreply.github.com>

lib/python/qmk/cli/__init__.py

@@ -56,6 +56,7 @@ safe_commands = [
 
 subcommands = [
     'qmk.cli.ci.validate_aliases',
+    'qmk.cli.ci.validate_keyboard_targets',
     'qmk.cli.bux',
     'qmk.cli.c2json',
     'qmk.cli.cd',

lib/python/qmk/cli/ci/validate_keyboard_targets.py

@@ -0,0 +1,28 @@
+"""Validates the list of keyboard targets.
+"""
+from milc import cli
+
+from pathlib import Path
+
+
+@cli.subcommand('Validates the list of keyboard targets.', hidden=True)
+def ci_validate_keyboard_targets(cli):
+    errors = set()
+
+    for rules_mk in Path('keyboards').glob('**/rules.mk'):
+        if any({'keymaps', 'common', 'lib'} & set(rules_mk.parts)):
+            continue
+
+        folder = rules_mk.parent
+        if not any(folder.glob('**/keyboard.json')):
+            errors.add(folder)
+
+    for keymap in Path('keyboards').glob('**/keymaps/'):
+        folder = keymap.parent
+        if not any(folder.glob('**/keyboard.json')):
+            errors.add(folder)
+
+    for error in errors:
+        print(f"{error}::Legacy target detected")
+
+    exit(min(len(errors), 255))