update regex

Signed-off-by: kminoda <[email protected]>

.github/workflows/cppcheck-differential.yaml

@@ -36,7 +36,7 @@ jobs:
 
     - name: Run Cppcheck on changed files
       run: |
-        files=$(cat changed_files.txt | grep '\.cpp$\|\.hpp$' | tr '\n' ' ')
+        files=$(cat changed_files.txt | grep -E '\.(cpp|hpp)$' || true)
         if [ -n "$files" ]; then
           echo "Running Cppcheck on changed files: $files"
           cppcheck --enable=all --inconclusive --check-level=exhaustive --suppressions-list=.cppcheck_suppressions --xml $files 2> cppcheck-report.xml