chore: add generation step for commit (#13337)

Adds a step to generate libraries when changing a librarian.yaml
workflow

[Fixes #6219](googleapis/librarian#6219)

Author: sofisl

.github/workflows/update_librarian_googleapis.yaml

@@ -68,8 +68,8 @@ jobs:
         new_commit=$(go run "github.com/googleapis/librarian/cmd/librarian@${version}" config get sources.googleapis.commit)
         echo "new_commit=${new_commit}" >> $GITHUB_OUTPUT
         echo "short_commit=${new_commit:0:7}" >> $GITHUB_OUTPUT
-    - name: Detect Changes
-      id: detect
+    - name: Detect Changes To Librarian.yaml
+      id: detect_librarian
       run: |
         git add librarian.yaml
         changed_files=$(git diff --cached --name-only)
@@ -79,8 +79,51 @@ jobs:
         else
           echo "has_changes=true" >> $GITHUB_OUTPUT
         fi
+    - name: Install protoc
+      run: |
+        set -e
+        VERSION="33.2"
+        curl -fsSL --retry 5 --retry-delay 15 -o /tmp/protoc.zip "https://github.com/protocolbuffers/protobuf/releases/download/v$VERSION/protoc-$VERSION-linux-x86_64.zip"
+        cd /usr/local
+        sudo unzip -o /tmp/protoc.zip
+        protoc --version
+    - uses: actions/setup-java@v4
+      with:
+        java-version: "17"
+        distribution: "temurin"
+        cache: "maven"
+    - name: Verify Java and Maven installation
+      run: |
+        java -version
+        if ! command -v mvn &> /dev/null; then
+          sudo apt-get update && sudo apt-get install -y maven
+        fi
+        mvn -version
+    - uses: actions/setup-python@v5
+      with:
+        python-version: "3.12"
+        cache: 'pip'
+    - name: Run librarian install
+      run: |
+        go run github.com/googleapis/librarian/cmd/librarian@latest install
+        echo "$HOME/java_tools/bin" >> $GITHUB_PATH
+      env:
+        PYTHONPATH: ${{ github.workspace }}/sdk-platform-java/hermetic_build/library_generation/owlbot
+    - name: Generate Libraries
+      if: steps.detect_librarian.outputs.has_changes == 'true'
+      id: generate
+      run: |
+        go run github.com/googleapis/librarian/cmd/librarian@latest generate --all
+        git add .
+        changed_files=$(git diff --cached --name-only)
+        if [[ "${changed_files}" == "" ]]; then
+          echo "has_changes=false" >> $GITHUB_OUTPUT
+          echo "No changes in libraries"
+        else
+          echo "has_changes=true" >> $GITHUB_OUTPUT
+        fi
     - name: Commit and Create PR
-      if: steps.detect.outputs.has_changes == 'true'
+      if: steps.detect_librarian.outputs.has_changes == 'true' || steps.generate.outputs.has_changes == 'true'
       env:
         GH_TOKEN: ${{ secrets.CLOUD_JAVA_BOT_GITHUB_TOKEN }}
         PR_TITLE: "chore: update googleapis commitish to ${{ steps.commit.outputs.short_commit }}"