also build merge sha

Author: mumrah

.github/workflows/build.yml

@@ -78,6 +78,10 @@ jobs:
   validate:
     runs-on: ubuntu-latest
     name: Compile and Check Java
+    strategy:
+      fail-fast: false
+      matrix:
+        checkout-ref: [ ${{ github.event.pull_request.head.sha }}, ${{ github.sha }} ]
     outputs:
       is-draft: ${{ steps.check-draft-pr.outputs.is-draft }}
     steps:
@@ -95,7 +99,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           persist-credentials: false
-          ref: ${{ github.event.pull_request.head.sha }}
+          ref: ${{ matrix.checkout-ref }}
       - name: Setup Python
         uses: ./.github/actions/setup-python
       - name: Setup Gradle