workflows: add check for generated AT Parser

Adds check for generated AT Parser lexer to determine
if it's up to date according to the regex source.

Signed-off-by: Mirko Covizzi <mirko.covizzi@nordicsemi.no>

Author: MirkoCovizzi

.github/workflows/check-generated-at-parser.yml

@@ -0,0 +1,42 @@
+name: Check Generated AT Parser
+
+on:
+  pull_request:
+    paths:
+      - 'lib/at_parser/at_match.re'
+
+jobs:
+  check-generated-at-parser:
+    runs-on: ubuntu-latest
+    name: Check Generated AT Parser
+    steps:
+      - name: Update PATH for west
+        run: |
+          echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          path: ncs/nrf
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get install re2c=3.0-1
+
+      - name: Generate lexer
+        working-directory: ncs/nrf/lib/at_parser
+        run: |
+          re2c at_match.re -o at_match.c -W --tags --no-debug-info --no-generation-date --no-version
+
+      - name: Compare lexers
+        working-directory: ncs/nrf/lib/at_parser
+        run: |
+          if diff -q at_match.c generated/at_match.c > /dev/null; then
+            echo "Lexer is up to date."
+          else
+            echo "Lexer is not up to date. Please re-generate the lexer and update the PR."
+            exit 1
+          fi