Add github worflow for clang-format checking (#221)

Make sure PRs pass clang-format check before merging.

Author: mansnils

.github/workflows/clang-format.yml

@@ -0,0 +1,66 @@
+# SPDX-FileCopyrightText: Copyright 2026 Arm Limited and/or its affiliates <open-source-office@arm.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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
+#
+# 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.
+
+name: Check clang-format
+
+on:
+  pull_request:
+    paths:
+      - ".clang-format"
+      - ".github/workflows/clang-format.yml"
+      - "Include/**"
+      - "Source/**"
+      - "Tests/UnitTest/Corstone-300/**"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  clang_format:
+    name: Check clang-format
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Install clang-format
+        run: |
+          sudo apt-get update
+          sudo apt-get install --yes clang-format-18
+
+      - name: Check changed source files
+        shell: bash
+        run: |
+          mapfile -t files < <(
+            git diff --name-only --diff-filter=d \
+              "${{ github.event.pull_request.base.sha }}" \
+              "${{ github.event.pull_request.head.sha }}" \
+              -- \
+              Include \
+              Source \
+              Tests/UnitTest/Corstone-300 |
+            grep -E '\.(c|cc|cpp|h|hpp)$' || true
+          )
+
+          if [ "${#files[@]}" -eq 0 ]; then
+            echo "No changed C/C++ source files to check."
+            exit 0
+          fi
+
+          clang-format-18 --dry-run --Werror "${files[@]}"