CrossBuild bump checkout action v2 to v4 to remove warning

.github/workflows/crossbuild.yml

@@ -17,7 +17,7 @@ jobs:
     steps:
       # step 1: checkout repository code inside the workspace directory of the runner
       - name: Checkout the repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       # step 2: generate build files and dump inside the workspace directory of the runner
       - name: Generate build files