Add rubocop rule for warning against backtick shellouts

Differential Revision: D70689678

fbshipit-source-id: b30c7833588a062b5982bc473fa4215329f5ff77

Author: Imanol-Mikel Barba

cookstyle/BacktickShelloutsInRecipes.rb

@@ -0,0 +1,25 @@
+# Copyright (c) 2025-present, Meta Platforms, Inc. and affiliates
+# All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module RuboCop::Cop::Chef::Meta
+  class BacktickShelloutsInRecipes < Base
+
+    MSG = fb_msg('Avoid using backticks for shellouts, use the execute resource instead.')
+
+    def on_xstr(node)
+      add_offense(node, :severity => :convention)
+    end
+  end
+end